GitLab can only fairly claim they are "open source" because they do have a fully-functional core of the project that is truly open source. Whether a license is

GitLab can only fairly claim they are "open source" because they do have a fully-functional core of the project that is truly open source. Whether a license is specifically OSI-approved, isn't the point. The point is that "open source" means something as a term, and that is widely respected as the standard. If someone claims a license to be "open source" when it doesn't meet the definition, they can and will be rightly criticized for being deceptive in using the term wrongly.