I don't like the idea of projects being dependent on a particular build tool, but there's not much I can do about it right now. I have a couple of ideas that I may pursue later. Maybe I could have a parent POM filter the project POM and then use the filtered version to build the project. That seems pretty hackish. Or maybe I could set up another execution of maven-assembly-plugin to produce an Eclipse project archive with the version resource already filtered.
For now, I think I'll let DRY slide and duplicate the version string in the POM and source. I'll just add comments to remind me to change it in both places.