Lots of people will view this as a sellout, but it isn't. The primarly difference between ESR and RMS is that ESR is pragmatic, and RMS is 100% principled and doesn't allow his principles to be modified by pragmatism.
ESR's stance is that the end (more openness -- and that means more Freedom, too) justifies the means (deal with more proprietary software now).
Lots of people will also claim that there is danger of a slippery slope here, that if we allow *any* proprietary software, then we won't know where to stop. I simply don't think that's true. As Linux increasingly dominates the marketplace and the world wakes up and realizes that Software Freedom just makes more sense, then we'll see a shift away from the new-old way of doing things. (The old-old way was when code was delivered to the customer with the compiled executable(s).)
I believe we'll see the same sort of progress in DRM and music/movie/etc. copyrights and the related P2P battles. As artists wake up and realize that the Internet enables them to survive in a different way than the current studio systems allow, many of these issues will morph and the current battles will go away. Why do you need a studio pushing your single in stores and on radio when the Internet can simply bypass these traditional advertising means and 'Net-based word-of-mouse advertizing can do all of/most of the work?
Of course, these processes will take years, and I think Linux-on-the-desktop will be the first one to see significant progress.
Especially if the community heeds ESR's advice now.