I was wondering this as well. According to Wikipedia: The EPL 1.0 is not compatible with the GPL, and a work created by combining a work licensed under the GPL

I was wondering this as well. According to Wikipedia: The EPL 1.0 is not compatible with the GPL, and a work created by combining a work licensed under the GPL with a work licensed under the EPL cannot be lawfully distributed. I haven't looked, but Light Table is using some EPL software for sure, starting with ClojureScript itself.