AIUI most FLOSS code is under copyright [0] the distinction being that the author(s) grant others a licence to use, copy and distribute under certain restrictions.
It seems that the author here wants people to be able to read the code, but not distribute it, primarily because he does not wish to tread on the toes of f.lux' developers.
[0] In fact, AFAICT unless a creator specifically and explicitly waives such, all work is copyright, because Berne treaty.
