The bit about WOTC saying you can only publish a product for one system, not 3.5 and 4.0, seems telling to me.
Rouse says "of course" they'd do this, since they want us to buy 4.0. Yes, I agree it's typical WOTC behavior.
But it seems outside the norm of behavior for similarly place corporations.
I don't see software operaring system vendors saying third-party software vendors can't make stuff that works on their current operating system and older versions -- or even competing versions. E.g., if you make Quark for Mac, you can't make it for Windows, or if you make it for Windows Vista, you can't make it work on Windows XP. In fact, they are usually heavily in favor of backwards compatibility.
With video games, I also see the same game coming out on multiple consoles -- I'm not sure if they ever do multiple generations of the same system, but I think some games do that.
I figure there's 2 reasons WOTC says my latest version and none other:
1) WOTC doesn't care as much about its end users. Backwards compatibility is the consumers problem, not the monopoly producer's.
2) WOTC fears 4e is an inferior product, so it'd frogmarching third parties and consumers into having no other choice. I'm not clear on whether they are not allowed to publish with non-WOTC games, like Hackmaster or Castles & Crusades, or if this is simply anti-3e, anti-consumer (no backwards compatibility), and anti-Paizo. If it says no Hackmaster if you want 4e, it sounds like an anti-trust issue to me. If the RPG industry was big enough for governments to care about (e.g., 1000x larger revenue), WOTC might be in the hot seat with the EU!