Heya Neophytos, long time.
From what I understand, there are three separate phases,
1, openacs developers decide to release a particular version or a package, so they twg it in some way;
2, something (maybe people, maybe code) looks for all the tags, "checkout"s those tags, and builds packages out of the code that emerges and inserts those packages into an area; and
3, the person who installs openacs decides to install a certain package, and looks for it in the area marked for their version of openacs.
I'm looking for 2.
-Jim