Making Maemo 100% free is a secondary goal for Nokia/Maemo. Nokia's goal is to make money by selling the tablet, so if there is a closed-source app or driver and it saves them the time of implementing it themselves, they'll do it so the device can be released sooner and allow the community to rewrite the app or driver if they see fit.

The other issue is that there isn't always an ability to open source drivers, especially for proprietary pieces of hardware because external companies haven't released their source or forbid it.

A 100% free Maemo is definitely a community goal. I don't think it's realistic to expect or demand a 100% open source operating system/apps from a company that is attempting to push the limits of design/use. Also, almost no companies out there open source their apps/operating system for their machines/devices because they are trying to make sure a rival doesn't just grab their source code and go "oh, that's how they did that cool thing we didn't... let's try that too".

There's always going to be a bit of a balancing act between giving away everything and trying to make money. I would cut Nokia some slack. They clearly WANT to make everything open source if possible and they have some clearly dedicated people pushing that (such as Quim).

Maybe someday.