To many people (including me until recently!) it's not "obvious" that permissions are totally different on these two OSes.
For more general rationale/advice on why avoiding the word "obvious" is important to fostering judgement-free learning, see https://spin.atomicobject.com/never-use-the-word-obviously/
* README.md: expand credit for original
Sudo was invented on Berkeley Unix on a VAX, and the current version is maintained by Todd Miller of the OpenBSD Unix project. It is thus correct to refer to the original as Unix/Linux as it is not a project originated by the Linux developers.
* Update README.md again, in ref to original sudo
Suggested by "omni" to have 'less occurrences of "Unix/Linux" in the README' - reads better this way.
Ross Wollman