Official releases should be tagged (i.e.: https://github.com/fabioz/Pydev/releases
), and looking at the history (http://pydev.org/history_pydev.html
), it seems there's no 3.1.x release (only 3.1 and then 3.2, for which there are pydev_3_1_0 and pydev_3_2_0) -- the pydev tags are always tagged with a 'pydev' prefix -- i.e.: pydev_v0_v1_v2 (the other tags are related to aptana studio or titanium from appcelerator and don't really make up to official pydev releases).
I didn't really notice that some aptana releases didn't even specify a prefix nor suffix, so, I can see how that may be confusing... I think I'll go ahead and remove those since they aren't really directly related to pydev and make things confusing (do you see any issue there?).