With a combination of legal paperwork and, perhaps it would be possible for them to retain a small enough piece of code as to block this, without having to retain ownership of the entire phone code.

That is phone as compared to the n900's mobile computer code.

I know it may not work 100% against backstreet forgers, but it would stop all of Nokia's commercial competitors from doing so.

Plus, who wants a ripped off crap bit of back street tech when they can have a Nokia platform to run it on.

What do they lose ? What could they gain. Any illegal deployments would act as free advertising of how good it is, another good thing.

Its a closed project for them, they can still protect their intellectual rights whilst allowing modification, they just retain sole right to hardware platform. ie, run it on anything other than a nokia and expect a solicitors letter in the post (companies of course, individuals do what they like, like we always do lol )