(Dgraph author) That's a good point. I think I'll load one instance up with the entire Freebase data, run it on freebase.dgraph.io, and blog about how and whys etc. Expect that in the next couple of weeks.
Dgraph follows MongoDB licensing. The clients are all in Apache, and the server code is AGPL. This doesn't affect anyone using Dgraph for commercial purposes; but if they make changes to the server code, they'll have to release them under AGPL. Blog post here: https://open.dgraph.io/post/licensing/