(coming from Choosing the right kind of function dispatch 
)
Wow, nice library @John_Newman! I particularly appreciate the good documentation (especially useful for alpha versions of libraries, I find).
One thing I love about dispacio is how defp accepts a higher-order function; it seems to fit really well into the dominant Clojure style and the function programming paradigm in general.
One question about the project’s licence - did you intend it to be under the MIT license or the EPL-1.0? I can find the text of the EPL-1.0 in the repository, but it’s (mis?) labelled as MIT. My preference is for the MIT one 