Comment 5 for bug 16128

> "cinepaint," [...] Unfortunately the project eventually halted

Cinepaint never halted development. there are working on a branch called Glasgow which amongst other things change the program to use FLTK instead of GTK. The cinepaint developers do make some efforts to make it relatively easy to part features from the gimp, you might want to contact them if you have specific questions.

The developers of the GNU Image Manipulation Program are working on a new image processing backend called GEGL to provide the greater colour depth you are hoping for.

Not sure how any of this fits in with Ubuntu, as I do not believe they are likely to take on the work of massively redevloping the infrastructure of the GNU Image manipulation program. I would recommend the Ubuntu bug team refer this upstream or (since upstream are already working on it) close this report.