I'm evaluating some of these technologies for one of my project. I need to use ECHO2 for the UI. And, I'm free to choose any technology for implementing my business services.
I read that Seam is more a glue between JSF and EJB 3.0. Right? Is is useful outside of this context? What other services of SEAM will be useful if I don't plan to use it with JSF.
There is no reason that Seam couldn't be adapted to other web frameworks, but JSF is the only one that really provides the richness of interaction that is needed for something as sophisticated as what Seam is doing. I am not familiar with echo2, so I can't say for sure that it does or doesn't.