This is OPAM 2.0.3 -- the OCaml Package Manager. The executables for x86_64-linux and x86_64-darwin are from https://github.com/ocaml/opam/releases/tag/2.0.3 In order to work properly, the underlying OS platform needs to provide standard build tools for C/OCaml development. Cygwin requires a separate package "opam" version 2.0.x. Makarius 23-Mar-2018