As far as I understand that is the opposite of how it works. The linux foundation was set up to receive funds from big business contributors - like Intel, Microsoft etc, who have an interest in the continuation of the linux kernel and wish to pay for jobs which didn't have a source of funding (i.e. Linus's job and other maintainer) and who wished to remain non-partisan. So these companies provide both code and money. That money isn't meant to be kicked back to profit-making companies as far as I understand.

Also, probably because grsec's code doesn't meet the standards. By almost all accounts, it pretty much sucks. I am unqualified to opine, but I trust the opinions of who are qualified - by being the people who try to implement it.