In order to package a Clojure project, I have to include clojure.jar which is an EPL licensed project, incompatible with the GPL. If I write my code in Clojure, but license it under the GPL, then that forces me to not package clojure.jar with it, making the installation process a huge pain.
I'm pretty sure that isn't a surety. See the accepted answer here https://stackoverflow.com/questions/11412160/java-libraries-... for instance. LGPL, in any case, would almost certainly be okay. Most people I talk to consider .jar's a dynamic link and dynamic links okay via the GPL but there are alternative interpretations and I don't think it has been tested one way or another in the courts.