This is the emails between the YouTuber YGK3D and Anycubic, it seems like they won't send 3D printers to reviewers who mention their GPL3 license violations.

tl;dr Anycubic uses open-source software for their firmware, but doesn't make it public as per license agreement, and they don't seem to be friendly to anyone who calls this out.

More info: https://www.youtube.com/post/UgkxIMpZTkXqFo0H6pDwhZpdYqMYvLhPvWA5?lc=UgxA-4LYvwrnonXuXsZ4AaABAg