Why the hate on D20? There are many systems that I don't care for, but I don't hate them. I have played D&D 3.x since it came out, my RQIII game having just recently falling apart after 15 years of play. D&D is not the same as RQIII. System does make a difference, but the new D&D is a good system, certainly much better than what came before.
Here are a few things to note.
Why do you refer to D&D or the D20 system as OGL? OGL is Open Gaming License. It is a license, it is not the system.
Mongoose RuneQuest is going to be OGL. It obviously is not going to be a D20 system. It is just going to be a game system with an Open Gaming License.
As for WotC/Hasbro. I do not like Hasbro in general, but WotC has been a solid advocate of RPGs. As an example. My local Game Keeper had one shelf dedicated to RPGs. When WotC bought the chain it immediately expanded to two shelves and was expanding. Of course as soon as Hasbro bought WotC all RPGs went on clearance and dwindled to nothing shortly before they closed the stores altogether. I can't help but not like Hasbro for that.
WotC and it's D&D/D20 system has brought about a renaissance in gaming. Just before D20 came out, RPGs still existed, but the number of people playing them seemed to be constantly dwindling. Now there are thousands more people playing RPGs thanks to the new D&D and the number is still growing. Now that they are playing they have the chance to discover the other games that are still out there. Other game systems that I like are Champions/Hero System for superheroes and ShadowRun. And now the new RuneQuest. They should have a new slogan for D20. "D20. The gateway RPG!"
Mongoose would not even exist if it were not for the D20 system and the OGL. How much money has Mongoose made on OGL D20 books? It is because of this profit and experience that they were able to get the licenses that they have now.
(That last is purely the speculative view of an outsider. I really don't know the full story of Mongoose Publishing.)
Back on topic.
For a setting I plan to revive my 3rd age RuneQuest game using the new rules. I will buy all the 2nd age stuff to flesh out history, but my 3rd age looks nothing like what Greg Stafford envisions now. That's what happens when you allow your PCs to influence the world that they live in.