There is no need to hide the l2jserver name, it's okay :D
Well, I'd say stick/use l2jserver, it's the best option. About those links, it's a SVN link used to download the sources. You must use Eclipse in order to download / manage / edit them :)
There is a wiki @ l2jserver, so you can follow it, there is everything how to download sources, complie and such.
http://www.l2jserver.com/2013/04/eclipse-and-svn-getting-started-guide/
There is more articles @ wiki, but I don't rly know the link. I'm not l2jserver user, but I saw it few times :P