I've got ActivityPub C2S (client-to-server) more or less working in my test site. It's safe to say that this functionality will be included in the Streams repository as soon as testing concludes.
Unfortunately you will not be able to use andStatus (the only known publicly available ActivityPub C2S client) as a client interface. What we will be offering is a generic service which complies with the ActivityPub specification and does not require any undocumented third-party APIs.
