Here is how the OGL could be scrapped. Please note, this is all silly and theoretical, and will never happen. It's the comic-book What If? type scenario only.
Step 1) WOTC entirely tables all D&D for several years and indicate they have no intention of reviving it any time soon;
Step 2) WOTC seeks and gets declarative relief stating that there is no longer any more consideration left in the OGL and therefore future licenses cannot be made (more on this below);
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As to consideration, ALL contracts (and a license is a type of contract) MUST have consideration to be valid. There is no choice - it's a required element of a binding agreement in the United States. Consideration means both sides must get SOMETHING of value out of the agreement.
I know that the law of consideration in the US is generally different from Anglo-Australian law - adequacy of consideration is not a requirement in Anglo-Australian contract law, whereas it is in US law as I understand it (and as you state it above).
Clause 4 states that the consideration that flows to WotC (as licensor of the SRD under the OGL) is the use by the other party of the OGL. What does the value of this consist in? Some of that value consists in promises not to use Product Identity (even to indicate compatibility), and I can see that if WotC ceased to publish D&D then that promise may not have value.
But even if WotC ceased to be in the FRPG publishing industry, wouldn't it still getting something of value from anyone taking up the licence, namely, the opportunity to use the OGC that the other party contributes? Unless the other party's work purporting to be under the OGL did not contribute any OGC, it seems that value (in the form of that opportunity) would be flowing to WotC.
Or is the argument that a mere opportunity in respect of an enterprise (FRPG publishing) that WotC has foregone does not have sufficient value to be genuine consideration?
I have a parking space in a desirable spot. I agree to allow you to use it for a year, for a fee.
You (a) sell your car (because you found an apartment that means you don't need the spot any more), or
(b) you get into an accident, and the car is totaled, and you can't afford a replacement.
In either case, you no longer have a use for the space. However, the value of the available space remains.
Would you be required to pay the fee for the remainder of the year? (I'm guessing yes.)
Yes, but as has been said this is about the validity of an extant agreement, not the valid creation of a new one.
Couldn't Hasbro just stop providing the OGL? No fancy steps. Just stop providing it.
If you already used the license, you could continue to use it. But, there doesn't seem to be anything to prevent them from taking the license away from potential new adoptees. The license is perpetual only when granted.
IANAL, but yes, you are missing something. Mainly, this:
The License: This License applies to any Open Game Content that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License. You must affix such a notice to any Open Game Content that you Use. No terms may be added to or subtracted from this License except as described by the License itself. No other terms or conditions may be applied to any Open Game Content distributed using this License.
and this:
Grant and Consideration: In consideration for agreeing to use this License, the Contributors grant You a perpetual, worldwide, royalty-free, non-exclusive license with the exact terms of this License to Use, the Open Game Content.
Since the SRD exists, and has the license attached to it, the license applies. The contributors grant a perpetual etcetera license, so it can't be withdrawn.
previously released OGC is out there and can be used with the corresponding license going forward. The license cannot be ended because the OGC is under the dictates of the corresponding license and the OGC cannot be undone because the licence grants the perpetual use of all OGC released under it.
As Staffan points out, the relevant clauses of the OGL seem to be 2 and 4.
Clause 2 ("The License") states that the OGL applies to any OGC "that contains a notice indicating that the Open Game Content may only be Used under and in terms of this License." Presumably such a notice could be rescinded. It is, in effect, a standing offer, and a gratuitous offer can be rescinded by the one who makes it.
Clause 4 ("Grant and Consideration") states that "In consideration for agreeing to use this License, the Contributors grant You a perpetual, worldwide, royalty-free, non-exclusive license with the exact terms of this License to Use, the Open Game Content." So there is no perpetual permission in respect of the SRD as such. Rather, once a person enters into the licence agreement with WotC (in virtue of using OGC from the SRD pursuant to the OGL) that peson gains a perpetual licence. So the licences enjoyed by all the 3PPs out there can't be rescinded.
If a publisher who was downstream, OGC-wise, from another publisher purported to rescind a Clause 2 notice then those who are upstream presumably would have standing to sue for breach of contract. (Because such a party would be in breach of the Clause 2 obligation to "affix such a notice to any Open Game Content that you Use.")
But as far as the SRD is concerned WotC is not downstream from anyone, and so wouldn't seem to be constrained in this way.