Clojure is on my list. When (if) I give up on Arc It will be the next language I'll learn and use. A lot of libraries from the start. Good performance (the JVM is fast once started). And, most importantly, Rich Hickey follows the language and promotes it. Arc had the great advantage that it had a community of users from the beginning. After its launch, a lot (relatively) of people were already using it. Despite this advantage, Arc hasn't reached the popularity that Clojure has today. Arc had the possibility of being a great language. That possibility has been wasted.
If you want to fork arc, you'd better change its name to break with the past. Make something new. I like the ideas behind snap. I only wonder how much time it would take to have a usable system. Sadly, I'm not able to really help :(