Only if it's a zero-sum game. Which it's pretty clear that it isn't. More support for a game = bigger and more active community = bigger total market size = more profit "pie" to go for.
The OGL, if handled well, makes hugely good business sense, growing the D&D market pie in exchange for letting others have slices of it. The huge mistake with 4E was removing the OGL, removing, at a stroke, a mass of support and enthusiasm for the game while, at the same time, leaving the old version to go its own way in competition (and then not even continuing to sell it, so missing out on free moey).