The eReader software is definitely never going to be "open" because it's under license from Adobe. Some of the driver software (for the Marvel chip, for example) similarly may be proprietary (at least in part) to Marvel, and similarly cannot be "open".

I also somewhat doubt any company would want to buy enTourage seeing as the world is going 99.9% with tablets, not dual books... Should another company buy enTourage, I'm quite sure we'd see a radical change in communications.