Originally this was aiming to be an index of all wikis (just as WikiIndex.org has become). It was started in May 2005 by a person using the name Oleg Popov, apparently based in Russia or Ukraine. But he or she didn't set it up properly (eg no "Search" function) and did not reply to approaches, even by email, after a few days.
It was later revealed that he or she had some link-spam purposes in mind, indeed the domain registrant also owned several pharmaceutical spamming domains.
Wiki4all contributors mostly migrated to other similar projects, particularly this one! There is probably still more material there worth copying. The wiki4all wiki succumbed to spam bombardment itself.