Where can I find permissibly licensed database of stars and constellations? I'm working on a game engine of sorts, and one thing I did for a previous game which was under the GPL was I had a night sky with the constellations visibly connected and I'd like to do that again.  I don't know where my data set originally came from but I do have a note that it was GPL, so it likely came from Stellarium, which is GPL licensed.  For this I need the dataset to come from the public domain, us government, permissively licensed, etc.

If possible I'm after the coordinates in the sky, brightness, maybe class and name, but also some mechanism to know which stars would be connected in classic constellations.  

I've found some data sets which contain the star data I'm after, though they would take some effort to parse and pull out the data I'm after, but I can't seem to find anywhere online, except stellarium, which provides star constellation connectivity. Any ideas?

I've gotten this list so far from what I can tell:


Stellarium: Has everything. GPL (Really restrictive) But has things like a constellationship file, i.e. https://github.com/Stellarium/stellarium/blob/master/skycultures/western/constellationship.fab
HYG: Great database, has everything I want, but licensed under restrictive CC 2.5 SA https://github.com/astronexus/HYG-Database No Constellations
BSC5: No explicit license, but created from NASA/ADC, data should be public domain.  Good data set, difficult to parse, no star connectivity.  (Best candidate for raw star database)
UCAC5: Navy (public domain), data set not geared for visible light.
HIP (used by Stellarium for stars) - Difficult to parse through, ESA (correct license) http://cdsarc.u-strasbg.fr/ftp/cats/I/239/hip_main.dat.gz


Are there any standards of what stars make up the primary connections in constellations?  Or does it just happen to be whoever puts it together?

P.S. If I ever do succeed, I will release the database (probably 3-4k stars is all I will need with connectivity) under the MIT license to permit inclusion in any commercial or noncommercial projects.
I have an idea how to do this, but it requires a few steps:


Yes, the IAU set down which connections make up the classical constellations, but I didn't see an easy way there to get their data.
Wikipedia has a list of stars by constellation. The stars there per list are many more than you need, BUT: the primary connectors of the constellation will always be made up by the brightest stars in a constellation, which will be the first entries in each list.
To access each list's first entries, I would recommend to modify the simple script from this question's accepted answer, which accesses a website and then datamines it for the interesting stuff.
Now not every constellation has the same amount of stars, but probably mining the 20 brightest ones each should be enough (brightness designators are the greek alphabet in order, $\alpha$ for the brightest, $\beta$ for second and so on.).
Then adding the connections: I don't have a good idea for that one. Possibly you have to bite the bullet there, grab a bottle of wine in the evening, and mark the connections by hand. 88 times 5-10 pair connections. Depending on the efficiency of how you mark the connectors in your database, you could be done in 1-2 hours. Still much faster than without any preselection. Should no other answer cover this step in a more efficient way, at least you could now get back to the IAU website and get the official connectors.