For what it's worth, I don't really see ebooks as nearly as big a threat to libraries as the oncoming "Age of Austerity." If government funding was not as big an issue as it is now, libraries would have a much easier time handling the transition to a digital era.
At any rate, copyright and libraries are clearly not in conflict, as demonstrated by the existing services. The same goes for paid rental services, which would have the exact same legal standing as, say, renting a DVD or a video game.
As to Overdrive: When a library uses Overdrive, the library is NOT licensing or purchasing books. What they're doing, basically, is paying to be a front-end for the national Overdrive service.
Overdrive will set up and customize a website for the local library, including checkout durations and book selections. Overdrive then apparently bills the local library for what local patrons use. I don't know how the "waiting list" works, but I'd presume the library can modify how many copies of a specific book they can loan. Overdrive may also set its own limits.
It may be possible for Overdrive at some point to offer some kind of "national rental service" direct to the public, though I assume this depends on the arrangements they have with the publishers. However, I don't think that some type of "Federal Digital Library" as a non-profit makes a lot of sense, especially since it disrupts the local character and involvement of public libraries (and since almost no one will agree to pay for it
)).