The CADPAT project was started by the Canadian Government in the 1980's. After tons of research, CADPAT finally became standard issue in the Canadian Forces in about 2000.
What I have been told by ASU (Area Supply Unit) is subsequently; the US Marines "noticed" the pattern and was interested in the technology. The technology to produce CADPAT was sold to the US Marines, and they in turn created their own called MARPAT.
[quote:1b8f5]Since 1996 the Canadian Military has put this project as one of its top priorities to address the largest deficiencies in operational clothing and protective equipment of our land force. Simply put: our uniforms and protective gear were out of date, behind the times, and actually hindered our military's effectiveness if called into action. New equipment, made and designed with new technological advances, combined with CADPAT (which was in development since 1988) would solve this need.
During its development, studies showed there is a 40% less chance of being detected from 200 meters away with CADPAT Versus Olive Drab. The results of these studies prompted the US Military to develop new uniforms based on the digital pattern as well, and as such, the Canadian government supplied information and manufacturers to the US for development of its own digital camouflage pattern named MARPAT.
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Although this site disagrees:
http://www.hyperstealth.com/CADPAT-MARPAT.htm
So really, I don't know. I know Canada has been developing CADPAT for a very long time. We either could have supplied the Marines with the technology, or they could have made it themselves.
All in all, the two uniforms are very similar. Their actually exactly the same, except for the colours used. The pockets, materials and buttons are identical.