The open source project trademarked the name of the project. Because it is trademarked, Amazon requires permission to use the name of the project.

This isn't unusual, many other open source projects trademarked the name of their project. Google has some guidance on why a project might want to do this.

https://google.github.io/opencasebook/trademarks/#unmanaged-...

Here is a list of open source projects whose name is trademarked by Canonical.

https://ubuntu.com/legal/trademarks