Where in zone 8 are you?
If it were my Zone 8 here near Seattle, I'd move it now.
I guess if you were in Zone 8 Texas, you could move it now also.
Japanese Maples are tougher than they first appear.
Mike

Yes: here the transplanting window for an established specimen (where lots of roots were going to be cut back) would be November through about February, with a later move being possible if the top still wasn't doing much yet.

If you just put this one in, so that you could still pop it out with most of the roots coming with it you probably have from now until it buds out in spring.

Meant to answer your personal email question but you do not have an email contact through GW!! You might want to change that if you do attempt email contacts :-)

Previous answers are good - any time the tree is dormant and the ground workable (not frozen or overly saturated) is a fine time to move/transplant. In my area (actually same as the two above), JM's do not emerge from dormancy until well into March. I'd say you have several months still to accomplish your move :-))