I think it's great to have a free software solution which wholly eclipses the competition. It's an incentive to use free software (use free software and get the best image codec in the world).
Yes, but the technology of "storing images" is never going to become the domain of free software. It's a little late for that.
If you're trying to drive widespread adoption of a competing file format, then don't GPL the only code that implements it. Make a brain-dead reference implementation with a license as unencumbered as you can stand. (Then code up an elegant implementation and GPL that.)
