Frankly, perhaps now is the time for enTourage to do a full source code dump to the community (other than items like the Reader software that is licensed to them by Adobe, etc.). Even source code written and owned by enTourage and not thought of as "open source". A formal SDK isn't even required by the developer community, as they know what they're doing and could easily try things out on the eDGe directly without an emulator, provided enTourage also fully enables debug and root access. The community would educate itself.
A source code dump could stir up a large enthusiast community, not to mention help speed up all kinds of bug fixes, enhancements and new apps.
I propose that enTourage would retain ownership of the code, but accept "suggestions" from the community where possible and fold that into official updates, sort of the way the Linux kernel works (I believe). Anyone could build their own eDGe distro, but the skittish among us can get our "official" update from enTourage.
This could spur more sales in academic circles to brilliant people that love customizing their device, and the increased prevalence of eDGes on campus could then fan the flames of sales to classmates. A wide open device may go on to encourage other markets to see the device as something that's unrestricted by the arbitrary whims of companies like Apple and the various phone and tablet manufacturers.
This would require a complete 180 degree turnabout by enTourage, but there's nothing to lose at this point.