Good good. If that "extra SSE boost ok" line hasn't shown up you might try shutting down the program and opening it up again. I'm almost certain G4's do the SSE boost if all is set up correctly.
Gromacs are indeed better than Tinkers on G4's. That's just a comparatively big job.
I just looked it up.
[00:20:09] Extra AltiVec boost OK.
Is the same as SSE on X86 cpus. So it's active. No worries, you just got a big steak to chew on :)