Well, it's called JuPyteR (my capitalisation), and originally supported Julia, Python and R. The exact provenance of the name is a bit unclear, but it's either deliberate or a happy coincidence.
Pluto.jl is also 'like Jupyter', but better and more popular among Julia users, as far as I know.
Pluto.jl is also 'like Jupyter', but better and more popular among Julia users, as far as I know.