The Sonic Retro SVN is now up, as evidenced by the link in the top-left corner now actually working. It'll lead you to WebSVN, the HTTP frontend for the SVN server. There's also a new forum directly underneath Sonic 2 HD which should be able to fill you in on more details.
The link isn't there on Retro Blue -- at least for the forums. The wiki links to it fine though (although the link to IRC is grayed out for me).
You need to add the links to HPZ Blue some time. Also, nice that you've finally got the project up & running, hopefully we can get some good shit from this.
All you need to get working now is that IRC link =P nice to know it's finally done - I might see what (if anything) I can check-in some time.
As a bit of an update, we now have Xenowhirl's S2 split disassembly up on the SVN for those of you who are interested in making improvements to it.