The "gel" process is actually a bit of chemistry, and sugar is an integral part of it, IF you are using SureJel or other common pectin. But... if you get some calcium-acid set pectin (one common brand is Pomona), you can add as much... or little sugar as you want. I made a big batch of cherry jam (canned, not freezer jam) once using Splenda, for a diabetic friend.
Sugar, however, acts as a preservative, so jams made without it will lose color and eventually flavor, much faster than jam with sugar. Freezer jam should deteriorate much slower than shelf stable jam.
I'd definitely try it with Pomona pectin, but definitely not with SureJel...
Let us know how it turns out!
Summerthyme