Yes :
http://www.cinepaint.org/
Cinepaint is a fork of GIMP used in the movie industry. Surprising to some, I know.
Cinepaint is a pile. It has higher bit depth than standard GIMP and being a subset tailored for some in-house cinema it is extremely long in the tooth.
GEGL replaces everything that Cinepaint offered and much more.
GEGL is nowhere near ready and seeing as it's taken 6 years to move off the toilet, figuratively speaking, when it actually can take a shower, get dressed and go to work then GIMP can talk about Non-destructive editing, etc. [most likely another year away at the rate that team works].
Two guys with Pixelmator and OS X mature Frameworks are running circles around GTK+ and GIMP.
With both systems and actually following and using GIMP since 1998 it's growth and maturity has been a snail's pace.
Cinepaint has been stuck on 0.22 for 4 years.
They've obviously been doing work and recently announced the delay of 1.1.
Lots of promise with GEGL:
http://git.gnome.org/browse/gegl/tree/NEWS
Great Features:
http://gegl.org/#features
when it's ready.
GIMP 2.8 has taken at least 2 years and several features were nixed to get it out the door.
GIMP 2.10 is the first release with major features people used to Photoshop will be thrilled to test. At the rate upon which the team makes a .2 update it's at least 12 months after the 2.8 impending release.
Blender [GIMP calls it its fellow project] is smoking hot and have native support for OS X.
Blender 2.6.2 has the Cyles Render Engine, Multi-GPGPU with CUDA/OpenCL support, UV Tools, Motion Tracking, Carve Booleans, etc:
http://www.blender.org/development/release-logs/blender-262/
and the BMesh entering the picture for 2.6.3 and currently in Trunk with all the hotness 2.6.2 provides it as a serious competitor to major proprietary projects.
The dev activity is massive and the donations are large. They've earned it.
GIMP is no Pixelmator. Two guys make tens of millions off of Pixelmator, leverage all the power of OS X with Grand Central, OpenCL, Quartz Compositing, etc., and to honestly proclaim it's a toy and GIMP is professional is way off base.
It'll be even more embarrassing if the guys at Pixelmator open up a mature extensions API ala Photoshop to open up a 3rd party add-on market.
The $29.99 for Pixelmator is obscenely low priced. I look forward to seeing what 2.1 adds to the app.
I look forward to GIMP 2.8 but my skeptic helmet has long forwarned me to be unimpressed with the ``feature additions.'' I'm glad they changed the UI, but that only took a decade of complaints to get it done.