> Are you equating "free" with "GPL-compatible", or did I miss something
> about nmap? (Last time I checked, nmap was FLOSS)

While the evaluation is terse, it is warranted: nmap is listed as GPL2
in my package manager for some reason, but happens to use a custom
license based on the GPL2: https://nmap.org/npsl/

One of the listed goals is "Prohibit redistribution and use of Nmap
within proprietary hardware and software products." This most likely
violates the four freedoms and thereby makes it GPL-incompatible.