False positive.
Same problem both with original Game Manager 0.3.3 and my mod.
I think i found what triggers antiviruses - GameManager.exe has embedded arc_conv utility, which is used to unpack Wolf RPG archives.
arc_conv is well known unpacker of game resources, but triggers antivirus heuristics.
I tried to compile arc_conv myself from source code which can be found here
You must be registered to see the links
And it is still flagged by almost half antiviruses on VirusTotal, same as Game Manager.
The only way to make Game Manager not to trigger antiviruses would be to remove arc_conv and ability to unpack Wolf RPG.
Since both Game Manager and arc_conv have their source code available, i don't see any reason to do so.