I don't think they ever went to "jail" at all, just home detention. They convinced a Federal judge that “the intent was not there to engage in illegal conduct”.

Gold & Silver Reserve CEO Douglas Jackson was sentenced to 300 hours of community service, a $200 fine, and three years of supervision, including six months of electronically monitored home detention.

https://en.wikipedia.org/wiki/E-gold#Resolution

It's Wikipedia, so it may not have been updated with all the relevant info.

There is also XAUT (Tether Gold) by the way.