they never claimed the UI would be community developed, did they?
imagine there really is a subsidized version that has a place for ads hardwired to the homescreen. wouldn't it mean that they'd need to block any possibility to boot into an alternate OS or else consumers would simply avoid having the ad by using mer instead of maemo? this would be more annoying than the ad itself, because it might lead to a design decision that affects both the subsidized and the non-subsidized variants.