Ok, there is for sure a closed source offering. Although, if you look at the data of the 1 millio top site on builtwith a strong oss share is clearly visible.

Ok, there is for sure a closed source offering. Although, if you look at the data of the 1 millio top site on builtwith a strong oss share is clearly visible. It goes without saying that wordpress has the overall largest share, which technically might not be considered a fully-fledged CMS...