We're still working out how to accept patches. There is no official process at the moment, so please let us know on the mailing list and we'll figure it out on a case-by-case basis.
We try to do one release every other week. Version numbers will use semantic versioning, although pre-1.0.0 we're using 0.x.y, where x changing indicates a backwards-breaking change and y changing indicates new features. Backwards-breaking means changing the BUILD or WORKSPACE file syntax or semantics. The output that Bazel prints during the build can change without the release being considered backwards-breaking, even though a tool that consumes Bazel's stdout/stderr might be broken by it.
Please let us know on the mailing list!