I have previously written a lot of code that is hosted on a public repo on GitHub, but it never had a license. It was written as part of my work while working for a non-commercial academic entity, and I would like to add a license before the link to the repo will be included in something that will be made public, potentially attracting one or two visitors.
This leaves me with a couple of questions:
- Can I just add a license after the fact and it will be valid for all prior work?
- Do I have to make sure the license is included in all branches of the repo, or does this not matter? There are for instance a couple of branches that are used to freeze the state of code at a certain time for reproducibility’s sake (I know this could be solved in a better way, but that’s how it is).
- I have myself reused some of the code in my current work for a commercial entity (internal analysis work, only distributed within the organization). Should this influence the type of license I choose? I am considering a GPL-license, but should I go with (what I believe to be) a more permissive license like MIT because of this?
Or just write an external document saying that all files in all previous revisions are available under whatever licence. There is nothing magical about a licence notice at the top of a file. It is just helpful documentation of the license. But you can document a licence anywhere as long as you are the owner of that code.