Nope, this registration fee is "paid" by the blockchain, in the form of initial funding of every Steemit account. When a new account is formed, there's a bit of STEEM in that account. Normally, a new user should pay the equivalent of that amount, but for now this is paid from the Steemit account, as a form of sponsorship.

Witnesses are not paying it directly, they just agree to its amount.