Yep, they are completely in their right to do so (though the content of the docs site is under Apache 2 so it's a slightly different license). Just wanted to point that out the work might have originated elsewhere.

Yes. Ionicons is released under the MIT license, which (AFAICT though IANAL) does not contain any attribution condition.

You have to include the original copyright notice. However, because of the Github templates, a lot of people don't fill in the copyright details. So in those cases derivatives are free to not attribute.

Thanks, missed that they failed to follow other parts of the license. That changes things quite a bit..