I'm actually a little foggy on this -- is this completely unrelated to the free software MusE DAW (https://github.com/muse-sequencer/muse), that also includes a sheet music editor as well?

I'm happy to see that the MusE DAW seems also to have resumed development after a very long hiatus / dry-spell. While not as feature-filled in most respects as bigger free software DAWs like Ardour, it has a more conventional piano roll interface with a few QoL features, which is why I preferred it for some time before switching to Ardour and getting over Ardour's sub-standard piano-roll.