The 4x4 Patterns are from the patternMaker software package.

patternMaker is useful for creating large numbers of patterns
for use with ARToolkit. It was developed by David Johnson,
Christopher Berthiaume and Bryan Witkowski.

More information about patternMaker please visit their website.
http://www.cs.utah.edu/gdc/projects/augmentedreality/download.html

The 4x4 patterns are distributed with this software under the GPL with permission.

Most of the other files in the directory are from ARToolKit.
As per the ARToolKit Readme
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The GPL-licensed toolkit.:

ARToolKit versions 1.0 through 2.x are available under the GPL. Please read the full text of the GPL prior to downloading and/or using the ARToolKit source code. Your downloading and/or use of the code signifies acceptance of the terms and conditions of the license. If you are unable to comply with the license terms, please immediately destroy all copies of the code in your possession.

Please be aware that while the GPL allows you to freely use the source code, it also imposes certain restrictions on the way in which you can use the code. Your attention is drawn particularly to section 2b of the GPL: "You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.", i.e. your software incorporating or linking to ARToolKit must also be open-source software, licensed under the GPL. Use of the ARToolKit in breach of the terms of the GPL will be subject to legal action by the copyright holders.