> I am a bit scared of a Linux ABI-compatible kernel with an MIT license.

What's the threat? Solaris/Illumos, the BSDs, even Windows, have all tried -sometimes more than once- to be compatible with the Linux ABI, and in the end they've all given up because the Linux ABI evolves way too fast to keep up and is underdocumented. Someday someone -perhaps TFA- will succeed in building momentum for a well-defined and highly functional least common denominator subset of the Linux ABI, and that will be a very good thing (IMO) regardless of their choice of license.

I guess you imagine that everyone will switch to Moss and oh-noes!-everyone-will-be-free-to-not-contribute-back!! So what?