I have just wrapped up the most recent commits into a new release:
You should be able to reference this tag from your opal installs in the usual way.
One minor (hopefully) change is that I have added a ‘release’ branch which is a bit more stable than the master. People seem happy enough merging to the master, and it might break from time to time, but the intention is the release branch will only get updated when tests have been passed. Comments on this very welcome!