The LICENSE[0] doesn't say that. That's merely Open WebUI's interpretation of their own license. Now, a judge would probably consider that estoppel, but you don't want to rely on that.
Using the license on its own, you effectively are saying:
- Don't use our branding to endorse your fork
- Don't remove our branding from your fork
The only way to satisfy both of these is to not fork.
Ugh, that's a real mess - they've clearly just invented their own clauses and tacked them on to the end of the previous 3 clause BSD license.
Technically, they're allowed to do that - the BSD-3 license is itself public domain - but it's usually a pretty bad idea. Have the new clauses been written by a copyright lawyer, or at least been vetted by one?
The fact that this is Open WebUI's second license change this year should be a red flag for anyone considering contributing to or relying on their software.
The forks will begin at the previous version though without having the branding requirements. Forking before the new version is what happens all the time.