Thats one of the things I hope WoTC answers soon... It says you can't redefine anything they've defined... But if you've already defined it, and then they come up with the new "official" defenition, is yours now redefining that official defenition? Or is it just offlimits to being redefined further (because the word is now in the SRD and allowed to be used by others.)
I'm of a mind that they meant the original SRD for 4e, not "anything we may ever make", but at the same time that's one of the core issues with the GSL vs the OGL.
1) They can redefine it at will, so you are subject to the will of the then current GSL. If they say "oh, that only applies to the three core books", that's fine, but later on they may change their minds when they change their staff...
For me, the other big thing:
2) I find the GSL to be a regular legal document drafted by lawyers with obtuse writing styles that lend themselves to furthering the legal profession by requiring lawyers...
The OGL was a VERY simple thing, there may have been a little confusion here or there, but overall comparing the two, the GSL has the stink of Corporate Lawyers, the OGL has a more inviting feel to it.
But again, the simple matter is:
Jade Ronin, Inc (a wholly owned subsidiary of Green Ronin) makes 4e products, some of which license GR's properties of Freeport, all of which are 4e only.
Games For The Goodman, makes their line of adventures, Classic Dungeon Crawls. It is made only for 4e, and no version of the same adventure is made under the OGL...
The limitations are:
1) you can't share product
2) WotC might get pissy and revoke your GSL (or not approve it in the first place)
Sure the corporate shuffle might cost a little more, but it's negligible.