Aside: I do computational applied math for a living, and haven't yet seen proofs.wiki before. Is it fairly new? An editable wiki just for formal proofs does seem like a decent idea.
http://proofs.wiki/index.php?title=Prerequisite:Copyrights&a... shows the copyright page is from December 6, 2014.
So, I assume this started around two months ago. The sparseness of content is not in conflict with that.
I think I would rather use a site that uses a formal proof checker behind it to verify committed theorems. It may get populated slower, but it can better be trusted.
"[The top-level domain name]... became available to the general public on May 26, 2014"
Probably. Sometimes comments get autokilled and mods will disagree with the algorithm, so they'll unkill them.