Hi,
I don;t think the mentorship program ever took off.
Right now, I think the best you can do is read the documentation, and ask specific questions you have here on the forums on in irc #openacs on irc.freenode.net.
http://catb.org/~esr/faqs/smart-questions.html is always a helpful reference for learning what type of questions will get a useful response.
I am not sure if projectopen has its own developer support forum or not, some people who visit this forum may have experience with projectopen.
Good luck and welcome!
