Hey you! Do you want access to bleeding-edge Synfig? Well, I have good news. Anonymous access to the Synfig Subversion repository for Synfig is now enabled! Here are the URLs to the respective repositories:
From the command line, to check out synfig-core, you would type:
svn co http://svn.voria.com/code/synfig-core/trunk/ synfig-core
Once you grab the code, you will need to bootstrap the build environment and then build the code.
At some point we may switch to git. dooglus maintains a git-svn repository of synfig and has a gitweb interface for it. While you are browsing the code, you may wish to refer to the source code outline and the source code glossary.