Unknown Skies is effectively "complete".
It will work with p. much any version of the game from 0.7 0.8 onwards (I think...), and will continue to work into the future unless the underlying generation method of the game itself changes significantly (which I fairly certain won't happen at this stage).
There is very little actual code in the mod, and what there is effectively self-contained.
It doesn't really need to be maintained anymore.
You can drop it into the game, and changing the version number in the mod_info.json file will allow it to work with no issues.
The link in the OP of this thread is the place to get it.
[mods]
Unknown Skies could probably go back onto the Index as an orange entry.
Might be worth having a dicussion about it at the very least.