I know that this is not directly related to Caspar, however it is something we are using in conjunction with Caspar, and this community always is able to offer help.
ARToolKit ( http://www.artoolkit.org ) is a FOSS augmented reality system, which is part of our system we've designed for live graphic superimposition with motion tracking, specifically for sports. Our luck with issue resolution has not been as great as it has been here as Caspar (which is being used for the chroma keying part).
Would anyone here, by chance, have any experience with ARToolKit? We are having some issues building from source on Windows, so any help that could be offered would be greatly appreciated. I do not know specifically, however I do believe many of the issues are with general programming, and not specifically with any of the AR functionalities, so any help with that would be great.