Many will disagree, but the way I see it they're fire and water. Commercial developers HATE to see quality OSS applications appear as they bite into their income, and the only way to battle that is to develop more complex/powerful/polished (and thus costly) software. This is aggravated by NIT users not as accustomed to paying for software than any other platform's users. Add to this the problem of DRM lack, which will further lower your income, and you will see what you have now on the NIT - the handful of commercial apps available for the NIT (some even in extras) are not exactly smash hits...

As for the flip side, if you make a push for commercial apps, any change you introduce to make commercial apps more competitive will undermine your OSS potential. OSS projects build the community from the savvy userbase, so if your userbase is driven to or naturally becomes a commercial app user, the OSS projects will wither (if you have a super-snazzy super-powerful super-supported super-quality app for 1$, who's going to manage to draw enough attention and community to build a quality alternative ?). In this scenario OSS projects whither to hobby projects, carrying little value to the end-users.

The worst case scenario is when you have both effects at play - in that case you don't have either OSS not commercial apps of adequate quality because neither community can fully exploit it's advantages.

Ceterum censeo the AppStore can't work with OSS in the Apple way.