Forum OpenACS Q&A: Response to Windows, AOLServer, and OACS
I think that on the issue of whether to port mod_nsd to Apache 2 or to implement FastCGI support, the latter would be a definite winner. Many people turn away when they hear about AOLserver but are definitely comfortable with Apache and/or IIS and besides there is just too much work to do on a working and reliable mod_nsd (not to mention the maintenance hurdle of keeping up with the AOLserver API).
Assuming that a FastCGI interface is written for AOLserver, I think the "appserver" AOLserver would best run under Cygwin (even though this means some work on Cygwin's pthread library).
Another note: right now I have no personal interest (or time :( )in mod_nsd or the FastCGI support, so unless someone pays me to do it, I'm not doing any work on them.