As far as JSF Ajax frameworks are concerned, there seems to be two major players: Ajax4jsf and ICEfaces. I don't know that either one is a true open source project (where developers are from multiple companies), but Spring isn't either, so I don't know that it actually matters. I think it interesting that both products don't seem to care about capitalization, but I digress.
Today, ICEsoft announced they've open-sourced ICEfaces. Was this inspired by Java going GPL?1 I doubt it, these things take time and it's likely that ICEsoft had this one in the cooker for quite a while. I do think it's interesting that the major JSF component vendors (Oracle, Exadel and now ICEsoft) have all open-sourced their products. Must be a tough market out there.
Apparently, ICEfaces works with Facelets, so it should work with AppFuse and Equinox. Looking through ICEfaces documentation and sample apps, they seem to be missing a straight-forward "here's how to integrate it into your existing application" guide. They do show how to modify your web.xml, but there doesn't seem to be a short, concise guide to what configuration settings you need to add to your faces-config.xml. I was somewhat motivated to write such a guide this morning, but lost motivation quickly as I realized it might be quite the effort. If someone wants to create the Maven bundles for ICEfaces, I'll try to carve out some time later this week to write up instructions for integrating ICEfaces into Equinox and AppFuse.
Unfortunately, integrating ICEfaces into your project is only the beginning. The hard part is choosing which is a better Ajax toolkit: ADF Faces/Trinidad, Ajax4jsf or ICEfaces? Trinidad and ICEfaces seem to be more about components, whereas Ajax4jsf is more about Ajaxifying regular ol' JSF components. So I think Ajax4jsf still remains, and ICEfaces looks like a better out-of-the-box component library than Trinidad. I guess time will tell.
Update: I forgot to mention Infragistics NetAdvantage as a JSF Ajax framework. OpenLogic decided to use Infragistics in the project I started for them. I was able to get it working in AppFuse fairly easily, but it's kinda ugly from a setup standpoint. They require you to copy a bunch of static files (images, stylesheets and scripts) into your project. Yech.
 Stephen O'Grady has an excellent writeup on this: And Sun Said, Set My Java Free: The Open Source Q&A.