Which e-book readers *don't* use Linux?

If you have a look at the Wikipedia page comparing e-book readers (http://en.wikipedia.org/wiki/Comparison_of_e-book_readers) right now you find almost only Linux variants including Android. The more efficiency you need, the more Windows will no longer be able to compete, as it can't be adjusted to the circumstances. I wonder when Microsoft will start to partially open source parts of Windows...