According to the GWT FAQ, you should be able to do this.
The heart of AJAX is making data read/write calls to a server from the JavaScript application running in the browser. GWT is "RPC agnostic" and has no particular requirements about what protocol is used to issue RPC requests, or even what language the server code is written in. Although GWT provides a library of classes that makes the RPC communications with a J2EE server extremely easy, you are not required to use them. Instead you can build custom HTTP requests to retrieve, for example, JSON or XML-formatted data.
I'm not aware of any projects to simplify the object serialization/deserialization logic though, if that was your question.
The client-side GWT code gets compiled to javascript, therefore it doesn't matter what server you use to serve it.
