The OGL was a very unusual license, and in some ways it kind of spoiled the publishers.
I've heard this said many times, the OGL "spoiled" the publishers. Muy perspective is quite different. The OGL was created with a specific purpose in mind: to create a "safe harbor" for third party publishers. In the absence of the OGL, publishers could have put out very similar products, but there might have been questions about what was permissible, which could lead to legal challenges that would be costly to WotC and fatal to most small publishers. The OGL never gave anything away but goodwill.
Virtually no game terms in the SRD are trademarkable and titles are generally not copyrightable. Game concepts cannot be copyrighted, only expressions. There are no patents in the SRD that are being licensed, and at this point, there is nothing left to patent. WotC did not invent elves nor regenerating trolls nor "halflings."
Effectively, the OGL served as a way of sidestepping what might or might not constitute "derivative content." It created a situation such that as long as you followed the rules, if you did create derivative content, you would not be sued and WotC would not have their IP rights weakened by a failure to do so.
I understand the OGL can be interpreted strictly as a business contract, but in a broader sense, it was a covernant. The purpose of the OGL was not to license some kind of original creation (like the Star Wars franchise or a a particular brand name like D&D) but instead to cover all asses. The few truly original variations on old themes (chromatic dragons, dark elves, clerics) long ago became assimilated into popular culture and there is no reclaiming them. I could go fire up Final Fantasy I right now and show you a fire-breathing red dragon, a frost-breathing white dragon, and a gas-breathing green dragon. That ship has sailed.
So in effect, it is WotC that has been spoiled. As originators of the OGL, they have grown used to the idea that they control the use of the SRD material. In fact, you need no license at all to create a wide variety of compatible products with little or no legal exposure. The only major obstacle is WotC's possible willingness to file unlikely suits in the hope of forcing the 3PP out of the game through bullying. Since WotC has retracted their offer as a safe habor, I can draw only two possible conclusions:
1. After years of debate, some folks in upper management still have not grasped the central issues at stake (the D&D trademark, versus the un-ownable right to create gaming products with may or may not be compatible).
2. WotC is prepared to sue 3PP publishers to dust and ashes, TSR style, in an attempt to maximize profits in the short-term by eliminating free market alternatives to their products, and is unashamed to take the role of a bully.
Whichever is the case, as both are dangerous possiblities, I would be leery of entering into any contract to WotC in which the licensee is not protected in some way from WotC's whims.
Keep in mind that WotC feels they are entitled, solely, to use the displacer beast... a creature which inspired by the coeurl, from Vogt's Voyage of the Space Beagle. They have forbidden others from referencing their unique, original interpretation of someone else's idea. While I do not think WotC is malicious or particularly greedy, it is clear to me that their IP policies reflect a continual tumult of business decisions, rather than a coherent philosophy based on artistic and business realities of the 20th and 21st centuries.
I could sell a vaccum cleaner bag and print right on the label, "Compatible with Hoover upright vacuum cleaners." Yet I am spoiled for thinking I can do the same for an adventure module? I can write books about elves and dwarves and such, drawing from the same sources as D&D... yet WotC presumes to tell me how tall an elf is and must be? The EU has told Microsoft, in plain terms, that they must allow others to write compatible software for their copyrighted OS and provide no impedence to them, yet WotC feels exempt from this basic pillar of efficient free markets.
What bothers me is not WotC's generosity, which has been reasonable in scope, but their presumption. It bothers me that they would make publishers jump through hoops who actually want to work with them and promote their brand, when less loyal 3PP can simply publish as they see fit, and as long as they practice reasonable caution, suffer no such restrictions. Whereas the OGL was a partnership of WotC, 3PP, and fandom, the GSL is imperial.
If the OGL was a bad business deal, then why was 3.5 so successful?