I maintain a project called "Coq Platform" which is essentially a set of opam packages. I would like to drag the license information for the ReadMe from opam. Almost all packages do have a license field. A notable exception are various OCaml core packages as the following output shows (packages with license field stripped):

Coq$ opam list --columns=name,version,license:
# Packages matching: installed
# Name                   # Version  # License
base-bigarray            base
base-threads             base
base-unix                base
depext                   transition
ocaml                    4.07.1
ocaml-base-compiler      4.07.1
ocaml-config             1
ocaml-secondary-compiler 4.08.1-1
ocamlfind                1.8.1
ocamlfind-secondary      1.8.1
seq                      base

Would it be possible to fix this, also for older compilers (for Windows compatibility reasons I am currently stuck with 4.07.1)?

In a private communication with @xavierleroy he suggested that opam lint should flag missing license fields - provided we agree that opam packages should have a license field.

For complex projects like Coq Platform, a consistent license field would be of great help for the maintainers and users.