Apache 2.0, but only to the extent of the actual code here. I didn't invent the Murmur[3] algorithm nor do I really understand it, I just ported it as best I could to c#. I picked Apache 2.0 because I want others to benefit from the work here, but not necessarily be able to "sell" the library itself (ie the compiled dll), but you are completely fine to use the library in commercial projects. I'm not a lawyer, so if you see a problem with the license, let me know and I'll fix it.