You can also get the sourcecode directly from the CVS server. For information about accessing the CVS server with an anonymous account check the documentation of SourceForge.net. You don't have to check-out all modules one by one - I created an alias called sim
for the list of all required modules.
Currently I don't use any branches since I only check-in code that is working - possibly some features are temporarily disabled due to a re-design - but it should still be safe to work with that code. Beside the advantage of working with the latest development state you could also immediatly get the latest bugfixes for which I'M not always doing a new release.