AJAX pains


I will be doing some heavy-duty web rich client work in the near future
for a project at work, and I’d like to ask if someone could recommend me
a full AJAX setup that:

a) Ties cleanly to a J2EE backend, possibly is even integrated into one
b) Works across a very large browser deployment base (IE, Opera, Mozilla
on the PC, Espian (?) on a TV set-top box, various PDA browsers (Pocket
PC IE, PDA Opera), possibly some smartphone browsers)
c) Is cheap / free to use - the project involves one server per
end-customer, which make the commercial ones with the per CPU fees into
the thousands of dollars price range unaceptable.

Thanks for any information in advance.

David V.
Fearing “Browser Wars 2.0”