If you're willing to wait a little while, there's a source code release for the full iD Tech 4 engine due mid-2009.
It'll give you far more power than JA will, at any rate, and you might actually have a chance at getting an MotS remake that captures the fun parts of the original's gameplay, which JK2 and JA totally failed to do.
Just a thought, and a better idea than a Half-Life 2 mod at any rate.
Oh, and.... Forumer? Yuck. Whoever recommended that to you, did it purely out of spite....