Open source Java ME
One of the benefits of Sun's decision to open source Java ME (along with the rest of the Java brand, but I am concentrating on Java ME), especially for an author and writer, is the ability to peek inside the code to understand what's going on. This provides a deeper understanding of the source code, and ultimately, a better communication to the readers than learning from the API.
Of course, in that regard, open sourcing Java ME has no benefit. The source code for Sun's implementation of the complete Java ME API stack has been available for a long time now via the Sun Community Source Licensing. Check it out here. The community source licensing is very similar to what the goals of open sourcing it would be. Of course there are differences, and I am no lawyer, so make your own judgements by looking at the community source licensing page here. It even allows you to modify the source code and contribute the changes back for 'the benefit of the community' without getting paid. Sounds very much like open source to me :).