At Pocket Gamer Connects San Francisco 2015, Ricardo Quesada, Chief Architect at Chukong Technologies, gave a talk on using open source libraries in your games.
He started by identifying distinctions between the different licenses that libraries are covered by, from purely open source to "ad-hoc" licenses.
All the libraries under the sun
He recommended avoiding the latter variety, warning that "nobody tests them, and it's unclear if you can use them", which could lead to potential legal problems after release.
Quesada then went on to list the many libraries available that he suggests using, including Chukong's own Cocos2d-x engine.
You can see all our videos from Pocket Gamer Connects San Francisco 2015 in this YouTube Playlist.