As I understand it, "Positions at CNRS" mean something different than it would in other countries, because, for a combination historical, social, and legal reasons, the French government largely funds research by hiring researchers directly rather than by giving grants through the universities at which they work.
I was discussing possibly making a 1-2 month visit to a French collaborator. (In the end, we couldn't get the timing and the funding to work out.) If I wanted a collaborator to visit me in the US, the funding mechanism would be that I would apply for a grant (eg from the NSF) or a supplement to an existing grant or a reallocation of funds in an existing grant to fund the visit. On the other hand, if a French person wanted me to visit him in France, the most common funding mechanism involves me applying (with his help and support) for a temporary one-month position from the CNRS.