the SRD did not become OGC as a part of WotC accepting a license agreement. The SRD became open content by WotC presenting it as OGC.
This statement is false. The phrase Open Gaming Content has no legal meaning except as part of the language used by parties to a licensing agreement to identify the subject matter of the agreement, as well as the permissions and obligations that arise under the agreement.
You are supposing that WotC, by making an offer to license its IP on the terms set out in the OGL v 1.0a, therefore changes or burdens in some fashion its rights in respect of its IP. Or to put it more simply, you are treating WotC as a legislator and the OGL as a statute. That is a mistake, and its leading you into confusion and incoherence. The OGL is an element in a private law regime, not a statutory regime.
how does the SRD become OGC? W (meaning, WotC) does not use any license agreement to make the SRD open content.
Yes they do.
Here's a link: https://media.wizards.com/2016/downloads/DND/SRD-OGL_V5.1.pdf
You can see there that WotC is offering to license certain elements of their SRD to anyone in the world, on the terms set out in the document known as the OGL v 1.0a. When someone takes up that offer, a licence agreement arises between the parties. The terms of that agreement are expressed using a concept "Open Game Content", which serves the function of both picking out those elements of their SRD that WotC are licensing, and of establishing the licensee's permissions and obligations.
The discussion (this thread) previously established Contributors are publishers of OGC, that WotC is a contributor (otherwise, how does the SRD become material for section 4?), and they did not become one by accepting the OGL.
In the above scenario, WotC are not accepting an offer. They are making one, on certain terms. When another party accepts that offer, they obtain certain rights from and against WotC. The terms of the agreement set out those rights. One of the concepts the agreement uses to set out those rights is "Contributor", which in this context is a label that describes WotC as the owner of the content - which is labelled, pursuant to the agreement, Open Game Content - that is being licensed.
Then, B accepting the OGL[WXA] means B accepting the offer of OGL[WXA]. Here, I presume that the license which is created by section 4, which copies all of the terms of the OGL, is not just a license but is also a license agreement which A must offer.
You are drawing a contrast between a licence and a licence agreement. But I can't tell what you have in mind.
Under the terms of A's contract with WotC, A enjoys a power to sub-license WotC's content to B, and is obliged to offer B that sub-license. That offer is stated in A's licensed work: the statement of the offer is comprised off the OGL text, the section 15 statement, and the notices of OGC and of Product Identity. If B does not want to take up that offer, B can easily decline it: just as one example, I've read Monte Cook's offer to me found in his Arcana Unearthed book, but I have never taken up the offer. Hence I have no licence agreement with Monte Cook. I've never taken up the similar offers I've seen in other 3PP's works either, and so I have no licence agreement with any of them, nor with WotC.
As a consequence of accepting this offer, B receives a license OGL[WXA][WXB], which is a copy of the terms of OGL[WXA], which is a license — and is a license agreement which B must offer.
You seem to be confusing a particular legally inert document - a set of words, phrases and sentences written out by WotC, copyrighted by them, and labelled "OGL v 1.0a" with two things that are not documents and are not legally inert: offers on certain terms, where those terms might be expressed by (among other things) setting out the text of the OGL; and agreements that arise when those offers are accepted, and which are on the terms set out in the OGL.
This would be like confusing (say) a model draft legislation with an actual enactment by a legislature which happens to use the words set out in the model (like my example of the cycling law that I set out in an earlier reply to you).
To say, is it meaningful to view of the OGL as both a license (permission to use, with limits) and a license agreement (a contract with considerations that awards a license)? It seems that the OGL becomes an actual license only after it is copied and granted by section 4. That is, agreeing to the OGL (as a contract) grants licenses which copy the terms of the OGL.
It can be meaningful, for some purposes (eg thinking about remedies for breach) to distinguish the contract parties enter into, from the licence that arises pursuant to that contract. For other purposes (eg in the case of the OGL, understanding termination for breach) there is probably no utility in drawing the distinction.
But there is no single the OGL
which is a licence, any more than there is a single the OGL
which is a contract. Each contract between two parties creates a licence in which one of those parties grants permissions and powers to the other, as well as imposing obligations on them. Paizo's licence to use WotC's IP in certain ways is not the same thing as Monte Cook's licence to do that, even though the two licences might be expressed using the same terms. (Again, this was part of the point of my example, upthread, of cycling laws which might be expressed using the same words but which operate in different jurisdictions.)
The most evident manifestation of the distinct character of the two licences is their different section 15 statements.
Typically, content becomes a part of OGC be being marked as such as a part of using other OGC, using the OGL. I used that to mean that the content was contributed. I should have said that the material was contributed while invoking section 4 because other OGC was being used. Can material from 3rd parties become OGC without invoking section 4? That is, without using other OGC?
What does "invoking section 4" mean? The OGL, and section of the OGL, is not a spell. Or a god.
Section 4 is a statement that contracting parties agree on to express the consideration that flows between them as part of their contract. It states that one - the offeror and licensor - grants a licence (over their works and/or the work of "upstream" parties who have granted the offeror the power to sub-license) and that the other - the acceptor and licensee - agrees to take on the obligations set out in the licence terms as well as accept the powers and permissions that flow from the licence.
Those obligations and powers and permissions are all rather technical. Setting them out using more-or-less natural language isn't trivial. So to help them do that, the parties define some terms they can use, and one of them is Open Gaming Content. This terms is used to "pick up" a notice that the offeror has attached to their work, identifying the material they are offering to license, and to explain a number of permissions, powers and obligations.
The concept of "contribution" is also used to help explain those permissions, powers and obligations. Because we are talking about copyright licences, potentially arising in relation to multiple works authored by multiple parties, it is helpful to identify the various parties whose works are at issue. The licence terms do this by describing those parties as Contributors.
A party does not need to use anyone else's licensed content in order to offer to license their own content - not in general, and not if they want to license their work on terms set out in the document labelled "OGL v 1.0/1.0a". For instance, Mongoose has licensed some of its copyrighted works, that deal with the RPG Traveller, on the terms of the OGL. So, obviously, has WotC!
there is OGC which is contributed directly with no concurrent use of section 4. That is, the SRD. Then there is OGC which was contributed with a concurrent use of section 4 for other OGC.
Really, this is a silly place to raise an objection. What matters is that WotC did not accept a license (to use OGC, at least in reference to the SRD), and I had no line showing them doing so. Whereas A and B do accept licenses, because A used the SRD and B used the SRD and used Z1 (A’s contributed OGC.)
There are core legal concepts that I am unsure that you grasp - offer, acceptance, contract, the difference between a legally inert text (such as a model law, or a model contract found in a book of precedents) and a text which expresses an actually extant legal relationship or state of affairs.
If you want to understand how the OGL licensing regime works, I strongly urge you to drop your presumption that WotC is a law maker that has simply "decreed" that certain of its copyright material has some novel legal status called Open Game Content. In the US, only a state legislature or Congress can do that. Read this post, and re-read my earlier replies to you, not with an eye to working out why I'm wrong or confused or not answering your questions, but rather accepting that I am setting out the legal state of affairs as it actually is.