How does the OCaml LGPL Linking Exception differ from using a non-copyleft license?

Question

The OCaml compiler and many other third-party OCaml libraries are licensed under the LGPL with a linking exception:

As a special exception to the GNU Lesser General Public License, you may link, statically or dynamically, a "work that uses the OCaml Core System" with a publicly distributed version of the OCaml Core System to produce an executable file containing portions of the OCaml Core System, and distribute that executable file under terms of your choice, without any of the additional requirements listed in clause 6 of the GNU Lesser General Public License. By "a publicly distributed version of the OCaml Core System", we mean either the unmodified OCaml Core System as distributed by INRIA, or a modified version of the OCaml Core System that is distributed under the conditions defined in clause 2 of the GNU Lesser General Public License. This exception does not however invalidate any other reasons why the executable file might be covered by the GNU Lesser General Public License.

Given that this exception "removes" section 6 of the LGPL, how does it differ in substance from using a non-copyleft license such as the MIT or BSD licenses? What advantages are there to using the LGPL with this linking exception, when compared to using the MIT or BSD licenses?

Answer 1

The main difference with using a permissive license, and also an advantage if you choose LGPL+linking exception, is that changes to the library (the OCaml Core System in this case) cannot be made under a closed-source license but rather must be made available under the LGPL (possibly with the same linking exception) when they are distributed.

In contrast, the permissive licenses allow that subsequent changes are licensed under a closed-source license.