You can stay up to date on the current developments by subscribing to the Manticore mailing list. It is generously operated by icculus.org. To subscribe, send a blank email to firstname.lastname@example.org.
Until we put together a bug submission web form, the best way to report a bug is to either join the mailing list and post the bug or to send one of the project maintainers an email.
Manticore's source can be checked out of CVS using the "pserver" method. To access CVS anonymously: (type this all on one line)
(password is "anonymous" without the quotes)
Web CVS is also provided here.