Can anybody recommend a (preferably open-source) framework for decoupling GUI from model in Java desktop applications?
I would strongly suggest you to try the ZK framework. I have not found until today such a srtong framework. In my company we have applied new projects within a few weeks using the latest patterns like MVVM. The style of programming is much like developing a classic 'desktop' app.
PS: I am in no way related to the ZK people. I am just using their framework.