The Glossarium finally arrived. Although most of the work was completed by Usener, he never published the work. In fact it was not published until 1977 in Rome and (as far as I can tell) never published again. Therefore it is in an unfortunate position to be written in the late 1800's but still has a copyright. This is, I suppose, one reason for it's rarity.
There are some modern edits, for example I was very pleasantly surprised to see a full equivalence table for the old listing of the P.Hercs to the one in modern use. Up to this point when I saw "VH2 I f.149" in Usener I had to do some digital digging in the Digital Corpus of Literary Papyri (in some cases unsuccessfully), but now we can look at the table as see that VH2 I f.149 = P.Herc. 1005!
Mostly it is a dictionary of Epicurean terms. This idea itself cannot be copyrighted, we will have to form a digital dictionary of Epicurean terms.