Hi Matthew,
As you've noticed, Dan created a GitHub repo that is indeed a mirror of the Mercurial repo. A few people, including myself, have been submitting pull requests there, both for master and for the py3 branch. Have a look at the closed pull requests to see what's been going on there specifically.
As for the state of the py3 branch, I've got the icomciv live-mode driver working, at least for the IC-910H, though others should work too. I can bring up the wxPython GUI and read all of the memories from the radio, including special memories. I can't write back from the GUI, though, since writing changes from a live-mode radio isn't hooked up in the GUI. I looked at it briefly, but my impression was that there's a design in mind that isn't all there yet, and I wasn't sure I understood the intent, so I didn't attempt to tackle it. On the other hand, I'm able to write changes to the radio using chirpc, so I know that the driver is working for write too.
More recently I've been waylaid by other projects, and haven't got back to getting more working on the py3 branch. I do want to pick up where I left off, though, at some point.
Martin.
KD6YAM