"Dev" is just a title like "Beta." It's meaning is dependent on the developers perception and yours. For instance. Microsoft has a long standing tradition of releasing "production" products which are clearly I would still call "dev" or "beta." Google releases "beta" products which I consider production. Microsoft sells their software, and so they want to get money for it as soon as possible by releasing a production version ASAP. Google gives their product away. They want to manage user expectations by calling something beta as long as possible. Marketplace is analogous to a Google product imho.