Maybe you can get one. I don’t see a nano mode in MELPA or GNU, and it doesn’t ship with Emacs. Nano is also much more likely to be installed than Emacs, especially since Apple stopped shipping Emacs with macOS.
GNU Nano is GPLv3 which Apple boycots (its v3 since 2007 according to Wikipedia). Tells us GPLv3 works :-) not sure what the license of Pico is. My first text editor was Q&A on MSDOS, it relied on F-keys, and on Windows 9x I got used to ctrl as modifier. Pico/Pine and later Nano was a natural successor, easy to learn. I use Vim and ST now.
Apache 2.0. I've used pine as a mail reader for well over two decades at this point, mostly on big old UNIX boxes. GNU nano always felt like the knockoff version.