I am a bit uncertain about this site.
At present it has mostly materials from Aster Data, the sponsor of the site.
Not that commercial sponsorship bothers me, any more than commercial vendors do. Commercial vendors being the people who sponsor standards writing, software projects and provide employment for those who participate in both.
Perhaps over time the site will grow to offer a wider range of materials on mapreduce.
That would be a real service to the community and would enable this site to function as a common ground.