Osada is a gateway server between nomadic and non-nomadic networks (such as between Zot|Zot6 and ActivityPub|Diaspora|Ostatus). A reference implementation is available at https://framagit.org/macgirvin
The purpose of Osada ("gypsy settlement") is to resolve the dilemma that software which was not designed around nomadic identity won't actually work correctly with software that is nomadic. The only other alternative is for all web communications software and protocols to be nomadic-aware and this is unlikely to happen.
In prior efforts such as RedMatrix and Hubzilla, federation with non-nomadic networks was offered as a choice. You could choose federation or nomadic identity. Choosing both leads to a situation where expected communications are not delivered and both federation and nomadic operation are flawed in basic ways. Osada resolves this basic dilemma by providing a gateway service between the two incompatible paradigms.
At a high level, Osada provides a non-nomadic server which can federate with all existing networks (to the extent that those networks permit federation; ActivityPub and Diaspora have limitations on their ability to federate third-party messages between incompatible protocols).
On the nomadic side, Osada does not allow nomadic operation itself, but it supports nomadic communication. It uses a Zot6 concept called "linked identities" to transfer information into and out of the nomadic network. The linked identity on the Osada side is not a clone and has a distinct non-nomadic identity. It can be bound to a nomadic identy on the Zot6 network. All federation and cross-protocol communication occurs at the bridge. If the linked identity relationship is severed for any reason (including failure/shutdown of the bridge), all bridged communications will cease.
Osada identities can be moved/relocated and connections on non-nomadic networks which support account moves will be retained. Connections on services which do not allow moves will be lost.
People inside the nomadic network will make connections to the nomadic identity. People on outside networks will make connections to the Osada identity and will be (likely) unable to resolve the internal nomadic identity as something they are able to federate with.