It's nice to give the flexibility to clients by exposing both. I haven't seen a problem with topic matching in my experience so far.
While I like the idea of adding flexibility, it'll probably also be harder on the debugging and maintenance side of things. We will keep the ZeroMQ gateway for external bus users, we may also consider a STOMP gateway that will do sanity checks on the fly if that becomes necessary.
One thing I found with AMQP vs STOMP is that it's possible for AMQP clients to (accidentally) emit "binary" message bodies, and then ActiveMQ does not translate or expose these as plaintext JSON for STOMP clients. It just looks like an empty message body to STOMP clients, or possibly garbage.
When using the fedora-messaging library, outgoing messages will be validated using a JSON schema and enforced to JSON/UTF-8. That should make it much harder to emit something broken. Received messages will also be validated, of course.
Aurélien