An experimental release of bnd(tools) 2.2 has a new feature called contracts. A recent blog post on OSGi.org explains who these contracts are for:
Though the OSGi has a very elegant package version model there are still many that think this is too much work. They do not want to be bothered by the niceties of semantic versions and just want to use, let's say, Servlet 3.0. For those people (seemingly not interested in minimizing dependencies) the OSGi Alliance came up with contracts in OSGi Core, Release 5.0.0. A contract allows you to:
1. Declare that a bundle provides the API of the given specification
2. Require that the API comes from a bundle that made the declaration
-- Peter Kriens
Read the rest of the article to get an idea of why these contracts work, even though they're seem strange to the experienced OSGi user.