Looks like your right, i cant find many similarities in the code. I had heard from a very good source that it was directly based on Harmony, perhaps only in concept it seems!
Thanks for pointing this out. Currently eating my own hat.
I don't know if it can even really be said to be conceptually based on Harmony. They're certainly both drawing tools using Canvas, but that's like saying Photoshop is based on MS Paint because they're both drawing tools on Windows.
Harmony is all about the procedural generation of images by interaction with previously drawn points. dA muro doesn't really permit that at all... which is a shame, as that's a technique with really interesting applications
In particular, the brushes behave differently. Note how in Harmony the currently-drawn line interacts with old lines, whereas in dA's one it only interacts with its own current segment.