I was very worried about this, because I have been helping a novelist friend of mine make a D20 game out of his world. We created about 12 classes, 8 races and heavily modified the magic system, among other things... We were thinking of maybe making up a .pdf of the final setting, including the SRD, for our buddies to download for some donation money, or maybe set it up as a print-on-demand.
And then, when we were 85% finished with our heavily houseruled game, the 4th edition announcement came up... And I for one had already resigned myself about not being able to adapt our game to 4th edition, since it was very likely that the new license would not allow our derivative.
So I am really glad to hear that we will be able to make this, as long as we don't include character generation rules or experience points to our work (which we weren't planning to do, anyway)