In other words, this site is pretty safe...
I didn't try it myself but there is a project on sourceforge that seems to be what you are looking for.
The project name is Paintbrush.
From the description on the site:
Paintbrush is a simple paint program for Mac OS X, reminiscent of Microsoft Paint and Apple’s own now-defunct MacPaint. It provides users with a means to make simple images quickly, something which has been noticeably absent from the Mac for years.
They have a number of screenshot on the site that looks ok.