LinuxMCE is a pretty big project. Not counting GSD devices, LinuxMCE's own code is already well over a million lines in hundreds of modules, with over 1,000 pages of online documentation, and in addition LinuxMCE also incorporates lots of other big open source projects like Asterisk, Xine, MythTV, Firefox, VideoLan, SlimServer, Kubuntu Linux itself, etc., all of which have special LinuxMCE 'wrappers' to allow them to work together seamlessly as a total home solution. For the brave of heart, you can also download modules by hand, and see all the dependencies and compatibility for each module.
You can browse the web based repository viewer. Or you can you do an anonymous svn checkout as follows:
svn co http://linuxmce.svn.sourceforge.net/svnroot/linuxmce/trunk/modulename
You can checkout all the software with if you use http://linuxmce.svn.sourceforge.net/viewvc/linuxmce/trunk/ as the repository location for the module name, or go to the repository viewer to find the name of the SVN directory for the module you are interested in.
Here are short instructions if you want compile your module with svn sources : Building from source.