FYI, the Nebula mobile client is source-available but not open-source. The devs from Defined Networking have been cagey about this and don't make this fact obvious, which makes me wary of Nebula.
Fair enough about the android mobile client... My use case only involves meshing linux appliances across various networks so we only need the nebula core binaries which are under MIT license
They could have just added a LICENSE file which stated you are not allowed to use to software without a commercial license. Instead they chose to be vague about it. Doesn't really inspire confidence.
https://github.com/slackhq/nebula/blob/master/LICENSE