Tokens per signup is variable. The currently advertised promotion is $10 worth of Steem Power. Given the price increase that means tokens per new account are reduced to 2-3. In the future the promotion might changed.

Also most of the 57 million is held as SP which means it is earning more tokens. Of course if the price declines then a $10 effective signup bonus would require more tokens too.

@iamnotback, the license for the blockchain prohibits forking. It is more of a shared source model than purely open source. Graphine is open source but the fairly extensive Steem modifications are not.