Source code fragments should have copyright and license statements

[mabraham]

We state that the lesson materials are CC-BY-4.0 in the text, which is good. However because we expect people to download and run the source files, that connection gets lost. We should copyright the source files by ENCCS, and state a license compatible with CC-BY-4.0.

Should we license that source code also CC-BY-4.0? Or e.g. MIT?

[wikfeldt]

source code is already licensed under MIT: https://enccs.github.io/intermediate-mpi/#software

But yes the source files should be copyrighted too for clarity