I had to wipe my Linux system and reinstall a clean copy. I added the grub-customizer. In doing so, I had to get it from "ppa:danielrichter2007/grub-customizer."
It said that I "added" that Unsupported, Untrusted ppa to my software sources.

Does this mean that from now on, I get software from "untrusted" daniel richter? I would like to of gotten the software, but not signed up to automatically get more stuff from Mr. Richter.

I'm sure he's a nice guy and everything, but, just like everyone else, I don't trust him.

On a broader question. Is there a command to use to get a piece of software, but not add that source from then on?

Thank you,
Chris.

You will only get additional software from that PPA if you explicitly install it. Without going into the details of update settings, you will receive updates to the software that you have already installed from the PPA, unless you disable or remove the PPA or choose not to install the update when offered.

To answer your broader question, you can disable or remove the PPA now that the software is installed. The program will remain installed (unless you uninstall it), it just won't be updated.