Does "Film Gimp" support CMYK color?
Now that I think about it, I'm not sure whether or not Film Gimp is even being actively developed anymore.
Film Gimp is now Cinepaint, and is due to be updated to the Glasgow edition for Windows any time now. But the latest Linux version is still available for download at http://www.cinepaint.org/
For Windows users who just can't wait for Glasgow, Jahshaka is a terrific stopgap piece of freeware. Comparable to a combination of Premiere and After Effects, its available at http://www.jahshaka.org/