Is my copy of Merlin legal?

[gaclark@m3.sprynet.com (George Clark)]

I recently downloaded a copy of the Merlin assembler for ProDOS from
Asimov, so my first question:

1. Is Merlin in the public domain or shareware, or is this a totally
illegal copy?

If it is indeed OK for me to have and use this software, then:

2. Can someone direct me to some documentation for it? I've tried various
searches for Merlin, Glen Bredon, Roger Wagner (found a Hyperstudio page;
not much good for Merlin), but all I've managed to find was a file of
supplemental information on the Caltech (I think) site.

TIA,
George Clark