My theory (which I can't write enough of) is that
WotC wanted to structure to
GSL so 3pps could publish modules, but not D&D variants (they don't wand someone to make to 4th edition version of T20). I don't think they intended the
OGL to allow them, but no one was thinking about them at the time. They made the
GSL so that it would not allow variant, and so they could close any other loopholes at will. They ended up with a license so restrictive lots of folks would not even publish adventured for it. We'll now get to see what they can come up with to allow modules, not variants, and that won't scare off 3pps entirely.
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