From their homepage:
Tux Paint is a drawing program for young children. It’s meant to be extremely easy to use, even for non-readers (with a little guidance).
Why and how did you get started?
In mid-2002, a friend from my local Linux User Group mentioned that he installed Debian Jr. for his kids, and was surprised to find the only drawing program included was Gimp‚ which we both agreed was a little hard to use, even for adults. Having written a number of open source games for Linux, I decided I could probably whip together something to fill the gap.
Who is the software’s intended audience?
Kids ages 3 to 12, though adults seem to enjoy it, too. It’s also been used for special needs kids and adults.