Desert Paint Lab will run on any machine that runs Java 1.42 or later. This should include every platform that runs ATITD. Anyone running Mac OSX should already have Java installed with the operating system. Windows and Linux users can find downloads here:
http://www.java.com/en/download/index.jsp
Desert Paint Lab will be made available under the BSD license, as soon as the software is done beta testing.
If you find any bugs in the software, feel free to contact Afrah, in-game, or follow the bug reporting instructions under Help > Contact, in the program.
You can download the package here:
http://lilly.csoft.net/~malkyne/atitd/paintlab/DesertPaintLab.zip
If you have a copy of Sigil's Practical Paint, you should unzip the files from the package inside the directory that Practical Paint is installed in. It should overwrite Sigil's obsolete colors.txt file with the corrected version. If you aren't running Practical Paint, you should create a new directory, and unzip the files into that directory.
There is a full tutorial available.