Well I certainly won't be downgrading my 4.4.2 app to 0.12.9 just to use AppD
However, I think that is a separate issue. If the AppD plugin was not compatible with 4.4.2 I'd be getting a warning when it installed (lots of libraries do this, especially with the huge version jump after the iojs merge). It would probably (hopefully?) still install and work.
A 403 means I'm not even able to get the installer package to attempt to install. It's being stopped at step one. This sounds like a problem with the repo.