How do I properly put third-party dependencies under MIT on my copyright notice for a published MacOS app on the App Store?

Question

If IconCast is the name of a close-sourced app I'm publishing that makes money, and AppIconSetGen, an open source library under the MIT license made by someone else that I made some changes to (which is also open source and under the MIT license), would the copyright notice that could be shown by pressing the "About IconCast" button under the "IconCast" menu when the app is focused be valid?

IconCast (C) 2023 Charles Yiu
AppIconSetGen (C) 2023 Charles Yiu & Attila Bencze

Do I have to say how AppIconSetGen is under the MIT license? Do I have to include a copy of the MIT license? How would I do it?

Thank you for clearing things up for me.

Answer 1

[...], would the copyright notice that could be shown by pressing the "About IconCast" button under the "IconCast" menu when the app is focused be valid?

Yes, the About screen is a valid and customary place to also show the copyright information of (open-source) third-party components.

Do I have to say how AppIconSetGen is under the MIT license? Do I have to include a copy of the MIT license? How would I do it?

You have to include a copy of the MIT license. You don't have to re-distribute AppIconSetGen under the MIT license, but you still need to include a copy of it in your documentation.

To make it clear that the MIT license is only relevant with regards to AppIconSetGen and not IronCast as a whole, you can structure your About dialog like this:

IconCast (C) 2023 Charles Yiu, licensed under <proprietary license>

Ironcast makes use of the following third-party software that has its own license
- AppIconSetGen (C) 2023 Charles Yiu & Attila Bencze, received under the MIT license

License texts:
<Proprietary license>:
<text of the license>

MIT license:
<text of the license>