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.
+1. Saw this earlier, thought "looks good, I should use it for a project", then read license and went "hahahahhaha no chance, not using a normal/standard licence is way too high risk for me, no matter the project".