I took the risk (some strangers reported it messing up their systems, but of course didn't provide any details), and apparently 32-bit GeSWall works swimmingly on 64-bit Windows 7:
That's a screenshot of the console that i manually started. I've told WinPatrol to allow its service and so far my system hasn't locked up or crashed. I guess all the "32-bit only. :(" reviews i read are false.
Disabling the GeSWall service, WinPatrol (noted to work in 64-bit Windows 7), Windows Defender, and even Windows Firewall, had no effect on Comodo HIPS and Firewall Leak Test Suite, CLT v.18.104.22.168's score of 190/340, though. (Only with Avira Free Antivirus active that score increased to 190/330 by blocking Coat.dll.)
As GentleSecurity appears to have died, perhaps Microsoft's DropMyRights is a sufficient replacement. Both should be able to be verified working by using Process Explorer to check whether the SetChangeNotifyPrivilige of a process is set to "Default Enabled", according to this thread. According to this page, DMR is only needed on XP, though, which will die in April 2014. Unless Microsoft reverted restrictive Vista features, which might have opened holes that today's drive-by downloads use.