Subversion development discussion takes place on the mailing list dev@subversion.tigris.org. You don't need to subscribe to the list just to submit a patch or two, but if you want to be involved with Subversion development on a regular basis, you should probably subscribe. It's high-traffic, but threading tends to be fairly disciplined, so you can ignore conversations you aren't interested in. For real-time chat, developers use the same IRC channel as everyone else: irc.freenode.net/svn.
The Hacker's Guide to Subversion contains information about submitting patches, learning your way around the code, interacting with other developers, project governance, etc. If you don't see the answers you need there, please ask on the mailing list or in IRC, we're happy to help.
With the release of version 1.1 Subversion program output can be translated. Discussion takes place both on the Subversion development mailing list as well as dedicated native language mailing lists (l10n-??@subversion.tigris.org).
Next to any information in the Hacker's Guide to Subversion pertinent to translating Subversion output, additional information can be found in
Currently available translations can be found in the po section of the repository. Please contact the development mailing list when you want to start a translation not available yet.
There is a Subversion BuildBot farm at http://www.mobsol.be/buildbot/. For more details, see here.
(Inferred from the design document)