In the abstract, I agree that having the OSI be the only one who can define open source is a little wonky. In practice, it turns out that everybody who makes this argument is doing it because they want to materially restrict what end users can do and are trying to pretend that their source-available software is "open source" for marketing reasons. Thankfully, it turns out that there are other groups making definitions that happen to dovetail into the exact same outcomes; I'm happy to consider definitions of Open Source from OSI, FSF, GNU, or DFSG ( https://wiki.debian.org/DFSGLicenses ).