I generally agree with what you're saying, although I think OpenOffice is a bad example - for a long time Sun did require copyright assignment for it so that they could release StarOffice. This doesn't seem to have helped OOo at all - in fact it appears to me to have contributed to its very slow progress. StarOffice hasn't gone anywhere either so I don't think it's been good for either of them.

I like the idea of a startup putting a slick frontend on OOo because it'd be just what I want - but it'd be a tough slog for them to make money from, so I'm not expecting to see it anytime soon.