It's not required, but it's generally safer to put a notice saying who owns the copyright and what license the file is released under at the top of each file. Some licenses like MIT, the BSD licenses, Zlib, etc are short enough that you can include the full license text in the notice, and others like GPL provide sample copyright header text to include. Here's an example of this from a random file in the SDL source code: https://github.com/libsdl-org/SDL/blob/main/src/video/SDL_bl...
Obviously Microsoft is still committing copyright infringement and in the wrong here. However, if the author had copyright notices in each file and then Microsoft stripped them out or changed the copyright information, it would make it harder for them to brush it off with "oops, we forgot to commit the correct LICENSE file" like I'm sure they'll do here.
Obviously Microsoft is still committing copyright infringement and in the wrong here. However, if the author had copyright notices in each file and then Microsoft stripped them out or changed the copyright information, it would make it harder for them to brush it off with "oops, we forgot to commit the correct LICENSE file" like I'm sure they'll do here.