I wrote in a sibling comment ‘I do get it — no-one owes me anything.’ No-one should be forced to do anything. Folks are and should be free to work on whatever suits their fancy.

But folks should also have a sense of duty or responsibility not to needlessly interfere with others. I am free to release a reïmplementation of ls(1). I’m free to extend it. But I shouldn’t change the meaning of ‘ls -d’ to delete all matching files, because it conflicts with POSIX. I shouldn’t change the meaning of ‘ls -b’ to overwrite matching files with nulls (blanks), even though POSIX doesn’t define it at all and in theory I am free to do so, because GNU ls(1) already uses it for printing C-style escapes.