ARToolkit comes in two flavours, the open source Version 2 with GPL 2 license and the socalled professional Version 4 which need to be paid. This page deals only with the free open source version.
It is available at Sourceforge and comes with Configure and make scripts which should make it easy to compile it on Linux. Unfortunally it didn't respects 64bit systems so it seems that the makefiles need to be touched and augmented with at least -m64 -fPIC for the compiler variables. Quit a lot changes, Makefiles are in the subdirs of subdirs of examples, utils and lib. While configuring you are asked to choose the right videosystem, choices are for example video4Linux and GStreamer. If you need to run a v4l2 device, it can be done via GStreamer framework.
When started, ARToolkit might complain of a bad palette. ARToolkit expects per default a RGB image from your camera but more often they return a YUV format.
Solution was to export the following environment variable:
This library uses markers for tracking of the position and rotation of objects in 3D space. It comes with several which can be printed and stick to surfaces. But its possible to create custom ones, tools are included but a more convenient way is the page http://roarmot.co.nz/ar/