InQ has a serious version compatibility issue. While it is understandable that a new server may need a new client for some new features, but even using the latest client may encounter the problem. InQ simply refuses to connect. As the result, one has to keep several different versions of InQ to just to connect different servers.
Jargon library doesn't has this much problem with versions, but it is merely a library.
This is a valid issue, and one we are considering. The design of our client API is such that clients are tightly bound to servers, and nearly any change in the server software requires a matching client version in order to guarantee proper communication. This is an issue experienced by all our clients including *nix and Windows based S-commands, inQ, MySRB, and Jargon.
The Jargon library packages all versions of the client/server protocol in one library. Our C-based clients however, would require multiple shared objects; in Windows this would be in the form of DLLs and preferablly, COM objects. In the past we did not elect to export a set of interfaces for our Windows-based clients. Due to concerns such as this one, we are now revisiting the issue.