The OGL and Open Source software licenses are superficially similar but fundamentally different. By accepting the OGL you gain permission to use some of WotC's copyrightet material in exchange for not doing certain other things which you'd normally have the right to do, such as using a name that WotC deems "product identity"
It does a bit more than that, it lets you reproduce the SRD whole cloth, as written. You know, WotC's copyrightable document that they are letting you use in exchange for following a set of rules, some of which are you have to share some of your toys too (or at least indicate which parts are your toys you aren't sharing). Basically it saves you the trouble of having to come up with new wording for literally every single rule in document. Most of them are complex enough you'd have to if Frylock is right.
Open Source licenses on the other hand do not ask you to restrict excising your rights , they let you use certain copyrighted material in exchange for explicitly taking certain action, usually sharing any modifications you make to the software and/or giving credit to the original creator.
Sure they do, you don't own the copyright on your new additions. You can't patent any sufficiently novel add-ons to the software. A whole bunch of stuff you could do you now can't. But again, in exchange you don't have to develop your software from square one, saving you time and effort in doing so.
As a thought though, if Frylock is right and the OGL is garbage, doesn't that mean that any company that use it and produced material based on it, like say Green Ronin, would be in for a problem since a huge portion of their material is derived fro the SRD?
And what about companies that sue the OGL but not the SRD? I've seen a few RPGs that like the idea, they copied the OGL and basically said this whole book, use according to the OGL rules. What does that do?