Julia does support REPL style development, and the little I have used it, it was effective for deep learning, text processing, and SPARQL/linked data clients.
Most of the infrastructure is there in the code, it just needs to be tied together, in such a way that juliac file.jl -o file.x results in a deployable (preferably static) binary.
The APIs are (these days) mostly web/REST-ish, though I'm starting to work on writing some wire-protocol stuff as well.
It (Julia) is an amazingly powerful language today. Excellent for data scientists and engineers, for deep and complex analytics. I am using it in a professional (e.g. paid) setting. Along side python, C++, and other things.