I've put together a development test that attempts to work around the long-standing bug in FreeFileSync 6.3 and later that renders it unable to be launched from other processes (menus, schedules, third party file managers, etc). This bug results in an error: "Cannot open file "GlobalSettings.xml". Error Code 32: The process cannot access the file because it is being used by another process. (CreateFile)" on starting the app.
This setup uses a second helper process to handle some of the file moves and break processes. Please give it a try and report back whether it works for you. Particularly if you've tried FreeFileSync 6.3 or later (the standard version without PAF) and had encountered this error on your system.
FreeFileSync Portable 7.9 Dev Test 4
Download 10MB / Installed 43MB
Note that we're packaging FFS 7.9. The official builds of FFS 8.0 and higher can not be made portable. The app locks itself to a specific relative path in an attempt to force end users to use the bundleware installer to install and upgrade the app. This appears to be done with closed source code rendering FFS 8.0 and later binaries not open source and possibly in violation of the GPL if the project has accepted outside code under the GPL and combined it with their closed source code.
7.9 Dev Test 4 (2016-06-29): Added 1 second pause before helper launches FFS
7.9 Dev Test 3 (2016-06-27): Downgraded to 7.9 to resolve install.dat lockdown (locked to specific relative path), disabled update check
8.2 Dev Test 2 (2016-06-27): Added second process break
8.2 Dev Test 1 (2016-06-26): First public test of new method