I'm a little confused. Was this code he released that allowed others to run a mixing service, or was it a mixing service ran by this guy, or is it some kind of distributed mixing service that cannot be controlled by anyone?

Which is debatable, but not illegal. SCOTUS has said so multiple times.

It would be interesting if this case goes to the Supreme Court.

Samourai wallet has been on HN several times, but this interview with the creator just before he goes to prison for writing open source code is very interesting.