[MENTION=22779]Hussar[/MENTION], I'm not sure why the subtly of this argument escapes you. I haven't seen anyone arguing, at least not without some serious qualification, that the OGL was "responsible" for the success of 3rd Edition, or that the DDI was not successful on its own terms. /snip
A quick comparison on the above - 3.X has OGL, sells very well.
4e has GSL, sales poor enough that WotC began talking internally about 5e in 2010....
So, yes, the OGL does make a difference.
The Auld Grump
See, right there. That's the first one in this thread that came to mind. I'm sure there are others. And, nicely ignores the fact that 3.5 COMES OUT 2 years after 3e, rather than being announced 2 years after the release.
If the OGL was so responsible for 3e sales, then why the failure? Why didn't they maintain 3e sales to the point where 3.5 was released later on?
See, the idea that it's the fans that gain in the OGL is true on the face of it. One of the most successful campaigns I ran was using the World's Largest Dungeon. Considering the sum total of my WOTC purchases for 3.5 was the PHB and DMG and I still managed to drop enough cash to fill a couple of shelves of books, it's not like I didn't buy OGL material.
But, I also don't mistake my buying habits for any kind of general trend. I was always the only one in my group to even consider 3pp. Heck, it was an uphill battle to get Dragon material used in campaigns that I played in but didn't DM.
I think people grossly overestimate how valuable the OGL is. They look at their own buying habits and then presume that everyone else is the same. But, then, if I look at my own buying habits, the OGL was a failure for WOTC. They only managed to sell two books to me out of the hundreds of dollars I dropped on D&D material.
After all, if I have a 3PP book of seafaring rules, why would I buy the WOTC offering? If I already have 3 Creature Catalogs, why would I buy another Monster Manual?
No one ever talks about the chilling factors of the OGL. It's always "OGL = More Sales For WOTC", when there are other interpretations that are quite well supported by the historical facts. If OGL=More Sales, then why didn't they? Why, during the largest boom in 3pp sales, did WOTC's sales fall?