You missed a crucial part of the license:

    subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all
    copies or substantial portions of the Software.

In the DMCA it's stated that his copyright is not credited, so they are in violation of MIT. If it's true that's a pretty low blow, it's so easy to use MIT code in a compliant way.

Ah, missed that, thanks.

If oh-my-fish didn't include the copyright and reproduction notice outlined in the MIT license, then yes, this is how the DMCA works.

However, the author cannot enforce that they don't use the 'wahoo' repo. If oh-my-fish attributes correctly, and includes wahoo's license, then they can use it.

> Permission is hereby granted [...] and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

In his DMCA notice on Github, the author states that the copyright was not left intact. I'm not certain whether he can void the whole license for "oh-my-fish" because of that or not.

That's exactly what the "subject to the following conditions" means. They have no right to use the code if the copyright notice provisions are not followed, following those conditions are what gives you the right to use the code.

If I give a license to use my code on the condition you pay me money, if you don't pay you also don't get to use my code.

I guess what I'm saying is: If they adjusted their code to comply with the license (i.e. add the copyright back), can they retroactively agree to the terms of the license?

Or in fact, does the creator of the original project have the ability to say "I no longer offer this license to you"?

He can't. Even if he authored all of the code in OhMyFish/Wahoo, which maybe be the case, the OhMyFish folk can rightly use the entire source of Wahoo granted they comply to the MIT license, which they didn't hence the DMCA takedown:

    The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

Yes, I was the one who initially noted that he didn't comply with that clause. I was wondering whether the original creator could retroactively revoke the MIT license permanently from the guy who abused the license.

Nope