My other question was are you aware of anyone using their in-house development to develop the middleware (DOR & DOF)? just curious?
I haven't actually heard of anyone developing their own middleware, although that doesn't mean there isn't anyone doing it. However, it seems to me to be a superfluous effort, since there are so many commercial and freeware HL7 brokers available. Even with the free stuff you can download off SourceForge you can do quite a lot, and in some cases you can even get some decent support.