Brunch is amazing. I was using Grunt in another project, but Brunch is so, so much faster to recompile changes, since it's very clever about caching.
Oh yeah, those sprites were in the repo as raster files, but we managed to move them all over to our awesome vector-graphics-in-the-database system just before launch. Check the DB dump to get a copy: https://github.com/codecombat/codecombat/wiki/Developer-envi...
(We did a ton of cleanup work before open sourcing, which managed to get our gzipped GitHub clone download from 203MB to 3.5MB.)
It might be hard to use these art assets in another game unless you take a lot of CodeCombat code on top of EaselJS to render the sprites directly from the vector graphics data, though, because of how they are stored: https://github.com/codecombat/codecombat/wiki/Surface#vector...
I could send you the old raster versions if you did want to use EaselJS for their animations but not go whole-hog with the CocoSprite solution.