The main issue with bootstrap-material is that this project is afflicted by the dreaded "developer thinks he needs his own license" bug[0][1].
It's effectively CC BY-SA-NC which is rather bold when you consider that it's adopting a design framework from Google for a css framework from Twitter.
[0] https://github.com/FezVrasta/bootstrap-material-design/blob/...
[1] https://github.com/FezVrasta/bootstrap-material-design/searc...