diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3b1b5483..8dadbad4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -306,6 +306,8 @@ logic/net/PasteUpload.cpp
 logic/net/URLConstants.h
 
 # Yggdrasil login stuff
+logic/auth/MojangAccountList.h
+logic/auth/MojangAccountList.cpp
 logic/auth/MojangAccount.h
 logic/auth/MojangAccount.cpp
 logic/auth/YggdrasilTask.h
@@ -368,8 +370,6 @@ logic/lists/ForgeVersionList.h
 logic/lists/ForgeVersionList.cpp
 logic/lists/JavaVersionList.h
 logic/lists/JavaVersionList.cpp
-logic/lists/MojangAccountList.h
-logic/lists/MojangAccountList.cpp
 
 # misc model/view
 logic/EnabledItemFilter.h
diff --git a/MultiMC.cpp b/MultiMC.cpp
index 6c88a6be..2c9e74dd 100644
--- a/MultiMC.cpp
+++ b/MultiMC.cpp
@@ -12,7 +12,7 @@
 #include "gui/MainWindow.h"
 #include "gui/dialogs/VersionSelectDialog.h"
 #include "logic/lists/InstanceList.h"
-#include "logic/lists/MojangAccountList.h"
+#include "logic/auth/MojangAccountList.h"
 #include "logic/lists/IconList.h"
 #include "logic/lists/LwjglVersionList.h"
 #include "logic/lists/MinecraftVersionList.h"
@@ -78,11 +78,13 @@ MultiMC::MultiMC(int &argc, char **argv) : QApplication(argc, argv),
 		parser.addShortOpt("quietupdate", 'U');
 		parser.addDocumentation("quietupdate",
 								"doesn't restart MultiMC after installing updates");
+		// WARNING: disabled until further notice
+		/*
 		// --launch
 		parser.addOption("launch");
 		parser.addShortOpt("launch", 'l');
 		parser.addDocumentation("launch", "tries to launch the given instance", "<inst>");
-
+*/
 		// parse the arguments
 		try
 		{
@@ -212,6 +214,8 @@ MultiMC::MultiMC(int &argc, char **argv) : QApplication(argc, argv),
 	m_qnam.reset(new QNetworkAccessManager(this));
 
 	// launch instance, if that's what should be done
+	// WARNING: disabled until further notice
+	/*
 	if (!args["launch"].isNull())
 	{
 		if (InstanceLauncher(args["launch"].toString()).launch())
@@ -220,7 +224,7 @@ MultiMC::MultiMC(int &argc, char **argv) : QApplication(argc, argv),
 			m_status = MultiMC::Failed;
 		return;
 	}
-
+*/
 	m_status = MultiMC::Initialized;
 }
 
diff --git a/gui/dialogs/AccountListDialog.h b/gui/dialogs/AccountListDialog.h
index 84ff8e0e..fe0c8773 100644
--- a/gui/dialogs/AccountListDialog.h
+++ b/gui/dialogs/AccountListDialog.h
@@ -19,7 +19,7 @@
 
 #include <memory>
 
-#include "logic/lists/MojangAccountList.h"
+#include "logic/auth/MojangAccountList.h"
 
 namespace Ui
 {
diff --git a/gui/dialogs/AccountSelectDialog.h b/gui/dialogs/AccountSelectDialog.h
index a539e7e9..6007253d 100644
--- a/gui/dialogs/AccountSelectDialog.h
+++ b/gui/dialogs/AccountSelectDialog.h
@@ -19,7 +19,7 @@
 
 #include <memory>
 
-#include "logic/lists/MojangAccountList.h"
+#include "logic/auth/MojangAccountList.h"
 
 namespace Ui
 {
diff --git a/logic/JavaChecker.cpp b/logic/JavaChecker.cpp
index 38bbf700..2b94fbb6 100644
--- a/logic/JavaChecker.cpp
+++ b/logic/JavaChecker.cpp
@@ -2,6 +2,7 @@
 #include <QFile>
 #include <QProcess>
 #include <QMap>
+#include <QTemporaryFile>
 
 #define CHECKER_FILE "JavaChecker.jar"
 
@@ -11,14 +12,15 @@ JavaChecker::JavaChecker(QObject *parent) : QObject(parent)
 
 void JavaChecker::performCheck()
 {
-	if(QFile::exists(CHECKER_FILE))
-	{
-		QFile::remove(CHECKER_FILE);
-	}
-	// extract the checker
-	QFile(":/java/checker.jar").copy(CHECKER_FILE);
+	checkerJar.setFileTemplate("checker_XXXXXX.jar");
+	checkerJar.open();
+	QFile inner(":/java/checker.jar");
+	inner.open(QIODevice::ReadOnly);
+	checkerJar.write(inner.readAll());
+	inner.close();
+	checkerJar.close();
 
-	QStringList args = {"-jar", CHECKER_FILE};
+	QStringList args = {"-jar", checkerJar.fileName()};
 
 	process.reset(new QProcess());
 	process->setArguments(args);
@@ -40,6 +42,7 @@ void JavaChecker::finished(int exitcode, QProcess::ExitStatus status)
 	killTimer.stop();
 	QProcessPtr _process;
 	_process.swap(process);
+	checkerJar.remove();
 
 	JavaCheckResult result;
 	{
diff --git a/logic/JavaChecker.h b/logic/JavaChecker.h
index 4488da66..291bf46c 100644
--- a/logic/JavaChecker.h
+++ b/logic/JavaChecker.h
@@ -1,10 +1,12 @@
 #pragma once
 #include <QProcess>
 #include <QTimer>
+#include <QTemporaryFile>
 #include <memory>
 
 class JavaChecker;
 
+
 struct JavaCheckResult
 {
 	QString path;
@@ -31,6 +33,7 @@ signals:
 private:
 	QProcessPtr process;
 	QTimer killTimer;
+	QTemporaryFile checkerJar;
 public
 slots:
 	void timeout();
diff --git a/logic/OneSixInstance.cpp b/logic/OneSixInstance.cpp
index b8d85ff5..337830a2 100644
--- a/logic/OneSixInstance.cpp
+++ b/logic/OneSixInstance.cpp
@@ -154,7 +154,7 @@ QStringList OneSixInstance::processMinecraftArgs(MojangAccountPtr account)
 	token_mapping["game_assets"] = reconstructAssets(d->version).absolutePath();
 	//TODO: this is something new and not even fully implemented in the vanilla launcher.
 	token_mapping["user_properties"] = "{ }";
-
+	token_mapping["user_type"] = account->currentProfile()->legacy ? "legacy" : "mojang";
 	// 1.7.3+ assets tokens
 	token_mapping["assets_root"] = absAssetsDir;
 	token_mapping["assets_index_name"] = version->assets;
diff --git a/logic/OneSixVersion.cpp b/logic/OneSixVersion.cpp
index e586402b..8ae685f0 100644
--- a/logic/OneSixVersion.cpp
+++ b/logic/OneSixVersion.cpp
@@ -165,7 +165,7 @@ std::shared_ptr<OneSixVersion> OneSixVersion::fromJson(QJsonObject root)
 		root.value("minimumLauncherVersion").toDouble();
 
 	// ADD MORE HERE :D
-	if (launcher_ver > 0 && launcher_ver <= 12)
+	if (launcher_ver > 0 && launcher_ver <= 13)
 		return fromJsonV4(root, readVersion);
 	else
 	{
diff --git a/logic/auth/MojangAccount.cpp b/logic/auth/MojangAccount.cpp
index b1acfb25..185c735c 100644
--- a/logic/auth/MojangAccount.cpp
+++ b/logic/auth/MojangAccount.cpp
@@ -23,6 +23,7 @@
 #include <QJsonObject>
 #include <QJsonArray>
 #include <QRegExp>
+#include <QStringList>
 
 #include <logger/QsLog.h>
 
@@ -52,15 +53,30 @@ MojangAccountPtr MojangAccount::loadFromJson(const QJsonObject &object)
 		QJsonObject profileObject = profileVal.toObject();
 		QString id = profileObject.value("id").toString("");
 		QString name = profileObject.value("name").toString("");
+		bool legacy = profileObject.value("legacy").toBool(false);
 		if (id.isEmpty() || name.isEmpty())
 		{
 			QLOG_WARN() << "Unable to load a profile because it was missing an ID or a name.";
 			continue;
 		}
-		profiles.append({id, name});
+		profiles.append({id, name, legacy});
 	}
 
 	MojangAccountPtr account(new MojangAccount());
+	if(object.value("user").isObject())
+	{
+		User u;
+		QJsonObject userStructure = object.value("user").toObject();
+		u.id = userStructure.value("id").toString();
+		QJsonObject propMap = userStructure.value("properties").toObject();
+		for(auto key: propMap.keys())
+		{
+			auto values = propMap.operator[](key).toArray();
+			for(auto value: values)
+				u.properties.insert(key, value.toString());
+		}
+		account->m_user = u;
+	}
 	account->m_username = username;
 	account->m_clientToken = clientToken;
 	account->m_accessToken = accessToken;
@@ -95,10 +111,24 @@ QJsonObject MojangAccount::saveToJson() const
 		QJsonObject profileObj;
 		profileObj.insert("id", profile.id);
 		profileObj.insert("name", profile.name);
+		profileObj.insert("legacy", profile.legacy);
 		profileArray.append(profileObj);
 	}
 	json.insert("profiles", profileArray);
 
+	QJsonObject userStructure;
+	{
+		userStructure.insert("id", m_user.id);
+		QJsonObject userAttrs;
+		for(auto key: m_user.properties.keys())
+		{
+			auto array = QJsonArray::fromStringList(m_user.properties.values(key));
+			userAttrs.insert(key, array);
+		}
+		userStructure.insert("properties", userAttrs);
+	}
+	json.insert("user", userStructure);
+
 	if (m_currentProfile != -1)
 		json.insert("activeProfile", currentProfile()->id);
 
diff --git a/logic/auth/MojangAccount.h b/logic/auth/MojangAccount.h
index 95f777ce..9eecbc4f 100644
--- a/logic/auth/MojangAccount.h
+++ b/logic/auth/MojangAccount.h
@@ -20,6 +20,7 @@
 #include <QList>
 #include <QJsonObject>
 #include <QPair>
+#include <QMap>
 
 #include <memory>
 
@@ -41,14 +42,13 @@ struct AccountProfile
 {
 	QString id;
 	QString name;
+	bool legacy;
 };
 
 struct User
 {
 	QString id;
-	// pair of key:value
-	// we don't know if the keys:value mapping is 1:1, so a list is used.
-	QList<QPair<QString, QString>> properties;
+	QMultiMap<QString,QString> properties;
 };
 
 enum AccountStatus
diff --git a/logic/lists/MojangAccountList.cpp b/logic/auth/MojangAccountList.cpp
similarity index 98%
rename from logic/lists/MojangAccountList.cpp
rename to logic/auth/MojangAccountList.cpp
index defa5d8c..0d13cd34 100644
--- a/logic/lists/MojangAccountList.cpp
+++ b/logic/auth/MojangAccountList.cpp
@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-#include "logic/lists/MojangAccountList.h"
+#include "logic/auth/MojangAccountList.h"
 
 #include <QIODevice>
 #include <QFile>
@@ -27,7 +27,7 @@
 
 #include "logic/auth/MojangAccount.h"
 
-#define ACCOUNT_LIST_FORMAT_VERSION 1
+#define ACCOUNT_LIST_FORMAT_VERSION 2
 
 MojangAccountList::MojangAccountList(QObject *parent) : QAbstractListModel(parent)
 {
diff --git a/logic/lists/MojangAccountList.h b/logic/auth/MojangAccountList.h
similarity index 100%
rename from logic/lists/MojangAccountList.h
rename to logic/auth/MojangAccountList.h
diff --git a/logic/auth/flows/AuthenticateTask.cpp b/logic/auth/flows/AuthenticateTask.cpp
index 966548ec..cc26cd1b 100644
--- a/logic/auth/flows/AuthenticateTask.cpp
+++ b/logic/auth/flows/AuthenticateTask.cpp
@@ -76,7 +76,7 @@ bool AuthenticateTask::processResponse(QJsonObject responseData)
 	// Read the response data. We need to get the client token, access token, and the selected
 	// profile.
 	QLOG_DEBUG() << "Processing authentication response.";
-
+	// QLOG_DEBUG() << responseData;
 	// If we already have a client token, make sure the one the server gave us matches our
 	// existing one.
 	QLOG_DEBUG() << "Getting client token.";
@@ -123,6 +123,7 @@ bool AuthenticateTask::processResponse(QJsonObject responseData)
 		// Profiles are easy, we just need their ID and name.
 		QString id = profile.value("id").toString("");
 		QString name = profile.value("name").toString("");
+		bool legacy = profile.value("legacy").toBool(false);
 
 		if (id.isEmpty() || name.isEmpty())
 		{
@@ -134,7 +135,7 @@ bool AuthenticateTask::processResponse(QJsonObject responseData)
 		}
 
 		// Now, add a new AccountProfile entry to the list.
-		loadedProfiles.append({id, name});
+		loadedProfiles.append({id, name, legacy});
 	}
 	// Put the list of profiles we loaded into the MojangAccount object.
 	m_account->m_profiles = loadedProfiles;
@@ -166,10 +167,11 @@ bool AuthenticateTask::processResponse(QJsonObject responseData)
 	// is it a good idea to log this?
 	if (responseData.contains("user"))
 	{
+		User u;
 		auto obj = responseData.value("user").toObject();
-		auto userId = obj.value("id").toString();
+		u.id = obj.value("id").toString();
+		QLOG_DEBUG() << "User ID: " << u.id ;
 		auto propArray = obj.value("properties").toArray();
-		QLOG_DEBUG() << "User ID: " << userId;
 		QLOG_DEBUG() << "User Properties: ";
 		for (auto prop : propArray)
 		{
@@ -177,7 +179,9 @@ bool AuthenticateTask::processResponse(QJsonObject responseData)
 			auto name = propTuple.value("name").toString();
 			auto value = propTuple.value("value").toString();
 			QLOG_DEBUG() << name << " : " << value;
+			u.properties.insert(name, value);
 		}
+		m_account->m_user = u;
 	}
 
 	// We've made it through the minefield of possible errors. Return true to indicate that
diff --git a/logic/auth/flows/RefreshTask.cpp b/logic/auth/flows/RefreshTask.cpp
index bd38eb10..16feac6e 100644
--- a/logic/auth/flows/RefreshTask.cpp
+++ b/logic/auth/flows/RefreshTask.cpp
@@ -67,6 +67,7 @@ bool RefreshTask::processResponse(QJsonObject responseData)
 	// profile.
 	QLOG_DEBUG() << "Processing authentication response.";
 
+	// QLOG_DEBUG() << responseData;
 	// If we already have a client token, make sure the one the server gave us matches our
 	// existing one.
 	QString clientToken = responseData.value("clientToken").toString("");
diff --git a/logic/updater/DownloadUpdateTask.cpp b/logic/updater/DownloadUpdateTask.cpp
index 3fe24482..d9aab826 100644
--- a/logic/updater/DownloadUpdateTask.cpp
+++ b/logic/updater/DownloadUpdateTask.cpp
@@ -239,13 +239,19 @@ void DownloadUpdateTask::processFileLists()
 	// delete anything in the current one version's list that isn't in the new version's list.
 	for (VersionFileEntry entry : m_cVersionFileList)
 	{
+		bool keep = false;
 		for (VersionFileEntry newEntry : m_nVersionFileList)
-		{ 
+		{
 			if (newEntry.path == entry.path)
-				continue;
+			{
+				QLOG_DEBUG() << "Not deleting" << entry.path << "because it is still present in the new version.";
+				keep = true;
+				break;
+			}
 		}
-		// If the loop reaches the end, we didn't find a match. Delete the file.
-		m_operationList.append(UpdateOperation::DeleteOp(entry.path));
+		// If the loop reaches the end and we didn't find a match, delete the file.
+		if(!keep)
+			m_operationList.append(UpdateOperation::DeleteOp(entry.path));
 	}
 
 	// Create a network job for downloading files.
diff --git a/mmc_updater/src/CMakeLists.txt b/mmc_updater/src/CMakeLists.txt
index 9b39bb83..d1a32755 100644
--- a/mmc_updater/src/CMakeLists.txt
+++ b/mmc_updater/src/CMakeLists.txt
@@ -34,7 +34,7 @@ endif()
 
 if (UNIX)
 	set(UPDATER_SOURCES ${UPDATER_SOURCES} UpdateDialogAscii.cpp UpdateDialogAscii.h)
-	add_definitions(-Wall -Werror -Wconversion)
+	add_definitions(-Wall -Wconversion)
 if (APPLE)
 	set(MAC_DOCK_ICON_CPP_FILE ${CMAKE_CURRENT_BINARY_DIR}/mac_dock_icon.cpp)
 	set(MAC_INFO_PLIST_FILE ${CMAKE_CURRENT_BINARY_DIR}/mac_info_plist.cpp)
diff --git a/mmc_updater/src/ProcessUtils.h b/mmc_updater/src/ProcessUtils.h
index 9fa10815..e0cc3dc0 100644
--- a/mmc_updater/src/ProcessUtils.h
+++ b/mmc_updater/src/ProcessUtils.h
@@ -5,6 +5,10 @@
 #include <list>
 #include <string>
 
+#ifndef PLATFORM_WINDOWS
+#include <unistd.h>
+#endif
+
 /** A set of functions to get information about the current
   * process and launch new processes.
   */