[vsl]

> It also seems to have some kind of threshold for code size, because for small contributions, it says that CLA was not required.

That's because all this copyright stuff is needed only for things that can be protected by copyright in the first place. One of the elements required is creativity of the work and if you only make a trivial change, e.g. Adding an obvious make file rule or adding a file to a project, that's not creative (there's just one obvious way to do it), so not protected, so not needing a CLA.