Thanks to everyone for the information. I guess it's fair to say a non-GPL version is feasible and likely in the future. I love the language myself and would continue using it myself regardless, but I wanted to clear this up before I start evangelizing it at work.
I'm interested to hear more about the pure Julia FFT. I had high hopes on using FFTS <https://github.com/anthonix/ffts>, but then I discovered it only handles single precision data.
