I agree pretty completely with Harald Welte's comments regarding Symbian. I encourage everyone to take a look at his comments.
We are in a very precarious time with regard to the freedom of mobile devices. We currently have no truly Free Software operating system that does the job, and there are multiple companies trying to get our attention with code releases that have some Free Software in them. None of these companies have pro-software-freedom motives about these issues (obviously, they are for-profit companies, who focus solely on their own profits). So, we have to carefully analyze what these proprietary software companies are up to, why they are releasing some code, and determine if we'll be successful forking these platforms to build a fully software freedom phone platform.
We thus must take care not to burn our developer time on likely hopeless codebases. I think Harald's analysis convinces me that Symbian is such a hopeless codebase. They haven't released software we can build for any known phone for sale, and we don't have a compiler that can build the stuff. It's also under a license that isn't a bad one by any means, but it is however not a widely used license for operating system software. Symbian's release, thus, is purely of academic interest to historians who might want to study what phone software looked like at the turn of the millennium before the advent of Linux-based phones.
Currently, given the demise of mass-market OpenMoko production, our best hope, in my opinion, is the HTC Dream running a modified version of Android/Linux. We don't have 100% Free Software even for that yet, but we are actively working on it, and the list of necessary-to-work proprietary components is down to two libraries. Plus, the Maemo software (and the new device it runs on, not even released yet) is the only other option, and it has quite an extensive list of proprietary components. As far as we can tell currently, the device may even be unusable without a large amount of proprietary software.
Even so, Android/Linux isn't a Dream (notwithstanding the name of the most widely used hardware platform). It's developed generally by a closed community, who throw software over the wall when they see fit, and we'll have to maintain forks to really make a fully Free Software version. But this is probably going to be true of any Free Software phone platform that a company releases anyway.
I'll keep watching and expect my assessment will change if facts change. However, unless I see that giant laundry list of proprietary components in Maemo decreasing quickly, I think I'll stick with the least of all these evils, Android/Linux on the HTC Dream. It's by far the closest to having a fully free software platform. Since the only way to get us to freedom is to replace proprietary components one-by-one, picking the closest is just the best path to freedom. At the very least, we should eliminate platforms for which the code can't even be compiled!
[ PC was kind enough to make a Belorussian translation of this blog post. I can't speak to its accuracy, of course, since I don't know the language. :) ]