Worth noting loud and clear that this project is obviously non-free despite of being disguised as GPLv3.
> If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term.
If you receive a GPLv3 licensed application from someone else who tried to add additional restrictions, then you can just ignore them, sure. However, this comes straight from the author, so what you actually get here are two conflicting rules given by the copyright holder. I'm afraid this can not be considered free unless a relevant jurisdiction's court judges otherwise.
definitely, he somehow thinks he can have two incompatible licenses on the same piece of software. Does that invalidate both of them?
If it was about two licenses, it wouldn't be a big deal (aside of being a pile of harmful bullshit, of course). But it's not - it's a single license with conflicting terms. A license is supposed to give the user an assurance of ability to use and/or distribute the software as long as they obey the stated rules, so if you get conflicting rules, such assurance is essentially useless.