Enjoy! @roman01la did a great job writing the original.
@aral the costs to run an instance are much more than technical/financial. As mastodon grows, the amount of time any instance maintainer has to spend managing content grows exponentially unless they whitelist, and maybe even then. If you want true federation, think about what tools need to exist to make small instances viable in the real world. This is very likely a Hard Problem with no financial incentives for solving.
VPE @ Drync. Rubyist since 2006.
A Mastodon instance for Rubyists & friends