No MorphOS UAE does not have JIT. There was an attempt made at a PPC JIT engine, but from what I read was a bit of a mess and nobody really interested that much in having one.
Well, you might need it for this since the RTG patch for TKG seems to crash with my mod almost immediately. However, to be fair, I found it crashed with the original game almost as quickly.
It would be really cool if the OS provided a lower level interface to it's own JIT that allows you to execute 68K code and then invokes native callbacks for various "illegal" operations, like hitting non-existent classic hardware, especially if it allows it to be "patched out" into a direct call in the emitted PPC code after the first time so that the overhead is minimised.