Using Parts of MIT Licensed Software

Question

I use an MIT licensed package to receive messages in a certain protocol. If I want to use a part of this package to build a new one (also MIT) which sends messages in that protocol (so it's 80% diff. from the original one, it just shares the translations part) do I still need to fork it and then delete most of it?

including without limitation the rights to use, copy, modify,

I assumed that MIT allows you to do anything with the code (and all files included) but I stumbled over this thread: What if somebody removed my name from MIT license

What's the correct way of doing this, adding my name to the MIT and keeping the other name? Or do I need to add the license to the files I used from the original repo?

Answer 1

What the MIT license requires is that you keep a copy of the license with the code you copied. The license does not specify how you need to copy the code, and it doesn't specify anything about you you license any code you add.

So, to answer your first question you are not required to fork and delete. You are welcome to use copy and paste to paste code into a new document, cp to copy code between directories, cloning using your code editing tool, or whatever mechanism you like.

The most common way to handle the license attribution would be to just add your name to the license headers as part of a list. Indeed, for any individual code files that contains both your code and copied code, that's the only practical course. However, if the code you're copying and your code are in different files, you can actually have separate copies of the license, some for the parts you copied with the other person's name, and some with your code and your name.