I'm more or less going off of the Wikipedia article:
http://en.wikipedia.org/wiki/Ulysses_(novel)
They mention that the 1922 first edition (same as 1921?) for some reason is out of copyright already (before the life+70 date), while 'some' of the other editions may go out of copyright in 2012. Apparently because the first edition was so screwed up, many of the subsequent editions which were 'edited' (possibly including the one with your end-notes), are copy-rightable as separate editions, and the scholars/publishing houses who made those editions retain the copyrights on those versions until who knows when...
Agree with lyric that it would be nice to get a definitive corrected edition - who knows, maybe some grad student will find it a fitting project and release it to the OSS community.
The Wikipedia article goes into further detail, but that's why I assumed Gutenberg was using the first edition.
There's also Gutenberg's own site, which says it's the pre-1923 print edition:
http://www.gutenberg.org/ebooks/4300 - click the bibrec tab.