So here are some questions when it comes to IP and WOTC, I didn't go through every page.
Much of DND's earlier editions were based on rules from wargames, do we know if TSR paid royalties for the use of those rules?
When WOTC acquired TSR, and came out with DND 3.0, they largely abandoned TSR's old rules. Many of the new rules the Player Handbook used bore striking resemblance to rules put forward to competing RPGs, particularly skill based systems, such as those put out by FASA and West End Games, these being TSR's competitors. For example, the presentation of the skills in the SRD with the difficulty class is very similar to the presentation in West End Games Star Wars 2nd expanded and enhanced edition (released prior to DnD 3.0) though that system used difficulty number. The chart changes a few names, and the type of die, but the target numbers on the chart are the same; this is different from the percentile die system 1e and 2e used for thieves or the non-weapon proficiency system used in 2e.
The function of ability scores also changed in a way that was closer to TSR's competitors than it was to the way ability scores functioned in 1e and 2e.
So how much of the IP WOTC is attempting to protect is actually original to WOTC or TSR and how much of it is material they borrowed and adapted from non-TSR games? Were royalties paid then, and are they paid now? If it isn't original to WOTC and TSR, on what basis is it being treated as a trademark?
Also, as games with no roots in DND, such as D6 adopted the OGL, how will this affect those properties, since presumably WOTC can't really claim they are WOTC's intellectual property on any basis? The OGL has functioned as a creative commons, even if it is not distinctly written as such. Does 5e borrow concepts from other creative common's games, and if so, does invalidating the license invalidate 5e's use of those concepts?