The source code for the Jikes RVM is stored in a Mercurial repository. You can browse the online mercurial repository at http://jikesrvm.hg.sourceforge.net/hgweb/jikesrvm/jikesrvm/.
A developer can either work with the version control system or download one of the releases. If you are interested in doing development of Jikes RVM you should probably use Mercurial instead of downloading a release.
This will clone the jikesrvm Jikes RVM repository into the newly created directory jikesrvm.
$ cd jikesrvm
If you are a not core developer you will not be able to commit push changes to the main Jikes RVM repository directly. Otherwise If you will need to place patches in one of the trackers.You can browse the online mercurial repository at http://jikesrvm.hg.sourceforge.net/hgweb/jikesrvm/jikesrvm/.want to contribute to the Jikes RVM, please take a look at this page.