http://bfeditor.org/ That is the original site, but after it was hacked the front page no longer has the links to it or displays the normal mod of the year stats.
Here's a mirror...
http://planetbattlefield.gamespy.com/View.php?view=GameInfo.Detail&id=133&game=3
Here's a picture of a DICE employee making SS with the editor.
You need Battlefield 2 to use it, but some users on the bfeditor forums found a way to install 2142 to make the editor think it was BF2 and still used it. I suppose you can do the same with Heroes but it should be even harder.
I've made a few maps with the editor, and if anyone is interested I'll show them. Porting the map from BF2 to BFHeroes is an easy process but you have to be a little experienced.