Yes, I've noticed this today as I routinely run a scan of the launcher with virustotal.
On friday the file was marked as clean but today (or yesterday, I'm not sure) they started "detecting" it as generic malware (hence the malware-gen name). "Generic" means they have not even looked at the executable themselves but their heuristic algorithm has decided that it's probable the file is malware
I've already sent a false positive report to Avast. Now, the only thing that we can do is wait. If you want to speed this up, you can also report a false positive yourself (to put more pressure on Avast).
Basically, you just have to write that you're using a launcher for an Arma mod. It's open source, its source can be obtained here ( https://bitbucket.org/tacbf_launcher/tacbf_launcher/src
) and it's packaged using PyInstaller.
As to the reasons for what's happening, my guess is that:
1) The launcher is written in python and then packaged to exe using pyInstaller.
2) Some malware is also written in python and also uses pyInstaller to generate an exe.
What does the Avast employee do? "Simple! Let's flag everything that uses those parts of code [pyinstaller libraries] as malware! Great, I can go back to watching cats again!".