Since
4E is derivative of
3E, and
3E had the
OGL, someone will be able to replicate the mechanics of
4E and release a product under the
OGL that will be somewhat compatible with
4E, regardless of what the
GSL says.
What they won't be able to do is use
WoTC exclusive IP, or use the d20 Logo.
I'm wondering if part of the drive towards feats with florid names (golden wyverns tail, or whatever) is to associate mechanics with fluff that
WoTC can claim as protected IP. In other words, a
OGL derived game like Grim Tales could pick up a
4E rules mechanic, but they'd have to change its name because the name is not Open. But that's just a wild guess.
At least, that's my perception of the situation. Would anyone care to correct me?
Ken