Hi Erik,
Agreed supporting "native" APIs would be a plus ! Would customizing "Jabber for Windows" (also known as JabberWin) be an option for your project ? For example on Windows the Jabber application supports the tel/im protocol handlers so other programs can click to call/chat easily, see
this post. Is this the kind of integration you want to add to your application, and JabberWin would provide advanced features (call control, presence ...) ?
Not sure what you mean by "thick control" ?
The web browser control mentioned earlier allows thick applications (Windows forms or WPF) to embed a web page with 2-way communication.
The browser plugin provided by the Jabber SDK adds softphone capabilities to the browser, available in any page to all users.
Hope this helps, Thomas