The video on the About Moodle page (http://moodle.org/about/) speaks of 'social constructionism'.
The page describing the educational philosophy which Moodle is designed to support (http://docs.moodle.org/22/en/Philosophy) refers to 'Social constructivism'. From the content of this same page, it would appear that the heading and its content should refer to 'Social constructionism'. This would be consistent with the video too.
Am I right or wrong? Any explanations?
These are two different things. Constructionism talks about about how the act of constructing things helps you learn, and constructivism describes how knowledge itself is constructed in an individual or social group.
In my view, "social constructionism" sums up both of these and more and is the term to use when talking about Moodle (or at least my intentions for it).
Others would summarise it with "Web 2.0" but that term wasn't around when I was developing my approach as a reaction against Web 1.0.