Not to necropost, but I'm happy I came across this thread. I was thinking up of a game system that was similar to XCom: Enemy Unknown and I did find one that used the Lumen system called "Intruder", but it wasn't crunchy enough for my tastes. I'm currently working on my own take using the Lumen system too, and I'm glad someone asked about the SRD.
I think this system is amazing to use a spine or core for what I have in mind.