I find that distinction very much of interest, and sure enough, RMS also has an explicit text available which deals with that matter more directly [0].

While free software protects the freedoms of the user only, copyleft software protects the freedoms of the developer as well. Both types of software are ethical (as mentioned in [1]), so it comes down to personal choice of the original author, who can use it as a tool to ensure their goals.

[0] https://www.gnu.org/philosophy/pragmatic.html

[1] https://www.gnu.org/philosophy/free-sw.en.html