No, we are not infringing any licenses
We spend a lot of time making sure we're not violating any licenses, and usually work with upstream early on. Charlie Smotherman got confused about how we had implemented music streaming and filed a bug reporting a violation. I'd encourage anyone who even suspects there may be a license violation to report a bug or contact us as soon as possible, but maybe hold off on the inflammatory blog posts 
We've contacted him explaining all this but he seems to not had a chance to update his claims so I'm bringing this up now.
Nobody on the Ubuntu One team commented on any of his blog posts either. Ampache seems like a nice piece of software and even some people on the Ubuntu One team use it. We chose to go with Subsonic clients (we are not using any of the server pieces as it doesn't fit with our infrastructure) because the API seemed to be very nice, the existing clients where very nice to use, and all upstream developers where friendly and happy to help us release the service.
I'm sorry if any feelings got hurt, but there's no need to lash out like that.
For future reference, the whole team hangs out in #ubuntuone on Freenode.