As you can see, the bug is fixed. If you look at the current resource URL you can see the "a4j_3_1_0" as a prefix.
I've patched a tomahawk 1.1.6 jar with a newest version of prototype script and this fixes the prototype problem in the short term. At future this shall be addressed directly either at richfaces or tomahawk, of course.
You can get the patched jar at http://rapidshare.com/files/56305024/tomahawk-1.1.6-np.jar.html
Actually I am also getting the same problem, i am using rich faces calender, I copied what you have told " alert(Prototype.Version); " but in the fire bug i am getting prototype is not defined what I have to do