Mike's right. Maemo is also "open source", but not really. You have to struggle with closed-source drivers that the open-source wouldn't be able to properly operate without and the appalling dependence on closed-source applications for the rest of the architecture. Hence the description of "open core" -- open-source software that cannot operate, or operates at a crippling, diminished way, without the closed-source software.

My concern is that MeeGo itself may be open-source, but it may not operate properly on Nokia devices without Nokia's idea of blessings upon consumers with lots of work to make sure you NEED to use closed-source drivers and applications that will undoubtedly come packaged in Nokia's firmware images.