You will need the OCaml compiler in order to build and use the OCaml PLplot bindings. OCaml includes both a byte code compiler (ocamlc) and a native code compiler (ocamlopt). Both of these are supported by PLplot.

Your computer may already have OCaml installed, or you can download it from caml.inria.fr. Several Linux distributions including Debian, Ubuntu and Fedora have OCaml binary packages available. Another route to obtaining OCaml is by using opam, a source-based distribution of OCaml and a number of OCaml libraries. opam can be retrieved from opam.ocaml.org.