OpenACS and dotLRN currently recommend a customized version of AOLserver that is available here:
http://uptime.openacs.org/aolserver-openacs/ The OpenACS version has some bugfixes and features, in particular, better support for internationalization. We're working on having these features added to the standard AOLserver distribution.
The version of nsxml that you found on SourceForge is newer than the version in the OpenACS distribution - I'm not certain if it has been tested with OpenACS yet.
