The wikipedia article has links to the official websites, and not to the scams: https://en.m.wikipedia.org/wiki/PuTTY
The website I was sketched out by (but tried it anyway, then got the scary error) was puttygen.com which had me install homebrew (whatever that is) and then do “sudo brew install putty”
The closest I saw was a .tr.gz file (i.e. a gzipped Tape ARchive) of Unix source code, but A) I don't know of their definition of "Unix" includes OS X / MacOS; and B) judging from your comments here, you don't seem like the type who would want to install software by downloading, decompressing, and compiling source code.
I'm thinking the people who told you to use PuTTY were assuming that you are a Windows user.