ejabberd development source code is published in the ejabberd Git repository, and also in the mirror ejabberd GitHub repository.
You can find instructions to get the development ejabberd source code in the ejabberd download page.
ejabberd-modules is an independent SVN repository just for ejabberd contributions. Check this tutorial for instructions.
Before February 2010, ejabberd was hosted in Subversion. You can check the migration announcement and some old pages: