I killed the server. People are still struggling with basic transacting, so I didn’t like the idea of adding another obstacle to getting transactions confirmed.
When it was operational, it was opt-in and over tor. Usage wasn’t enough to make it worthwhile yet. There is less than 1 transaction per minute in Grin, so even if every transaction used GrinJoin, the server would have to wait 15-30 minutes to have any kind of meaningful aggregation.