So...was doing some reading after I saw the post about by RAZR in the community ban-list...
And this is only worth the effort if people think OA is big enough...
but there's a project out there called ETACE, ET AntiCheatEffort...sounds punkbusteresque, but open-source.
I have no idea how it could be made to fit with the GPL, since it definitely has "closed-source" pieces to it, but...it might be something to think about if OA grows big enough.
http://etace.ycn-hosting.com/