The Definite Article

I've heard people say "the NSCL," and I've heard people say just "NSCL"; likewise with "GSI" and "the GSI." So which one is it? Here we present the results of a literature Wikipedia search on the topic of "The Definite Article and Fragmentation Facilities" (see below).
 
Incidentally, if you're going to use the definite article before an abbreviation in another language because the thing-it-stands-for requires one, should you then say the abbreviation's letters in the other language's pronunciation system? Comments (anonymous or otherwise) weighing in on this topic are quite welcome.
 
Locally, it's the National Superconducting Cyclotron Laboratory, and "the" isn't in the acronym (naturally), so I'm going with the NSCL.
 
Here's a quote from the relevant Wikipedia article: "The Gesellschaft für Schwerionenforschung mbH (GSI, Association for Heavy Ion Research)"--this doesn't seem to show a clear-cut choice for the GSI or just GSI.
 
According to Wikipedia, RIKEN stands for "The Institute of Physical and Chemical Research" and thus is RIKEN.
 
Also from that great fount of knowledge, Wikipedia, GANIL stands for "The Grand accélérateur national d’ions lourds, or Great Heavy-Ions National Accelerator"--I'm not sure whether this means it's GANIL or the GANIL. I have, however, never heard anyone use the definite article to refer to it, so I'm going with GANIL.
 
Also, is it "the arXiv," or is it "arXiv"?
 
This is a tiny little thing, and it's confusing me all out of proportion to its significance, but I like to know what things are really called! Expert opinions on the topic are appreciated.