Yeah, that line’s a real gray zone. Public domain code is free to use, but most open source is under licenses that still give you rights to copy and modify. Once you mix proprietary code or add your own significant changes, you can claim ownership of that new work, but you still owe the original license. It’s all about the license terms, not the file itself. So the blur is where the license says you can do anything versus where it imposes conditions. It’s a good angle to dig into.

Sure thing. First grab the license files from the repo roots—look for LICENSE, COPYING, or LICENSE.md. Then copy the key clauses that talk about modification, distribution, and attribution. For each high‑profile project, jot down whether it’s MIT, GPL, Apache, or something else. Next, search the code for “copyright” or “notice” blocks; those usually pin down the ownership and any required attribution. Finally, map any code you plan to copy into a new project: if it’s under an MIT or BSD, you’re good to go with minimal attribution; if it’s GPL, any derivative must also be GPL. That’s the skeleton we’ll flesh out.