I have nothing to do with the authors of this book/page but this attitude is why I don't do free software.
What attitude? The selflessness of the developer for giving away the software, or the gratefulness of the user who got exactly what they wanted? In either case, I struggle to see what repels you.
One, a Gmail that I’ve had forever, is my “public” email that’s just filled with junk.
The other is used for stuff like banks, utilities, etc. and I protect it fiercely from spam of any kind.
It’s easy to know what to pay attention to that way and made my life more enjoyable, or at least easier to parse.
For services and what not I know and trust I go with a regular alias with my domain for this purpose. And I have service specific aliases such as foo@example,com so I can delete the alias if necessary which is rare.
Then there the quick thing that you can do with any address for separation of concerns with foo+bar@example.com so if your email address is foo@example.com, just make a quick and dirty instant alias by signing up with, say, foo+bar@gmail.com.
I give away my recent eBooks for free (and also provide a link where people can pay if they want). Because I am an author, I have met many interesting people and have had job opportunities appear without my having to search for them. Also, I love the process of writing. BTW, I started out writing for conventional publishers (10 books) and transitioned to this Creative Common self publishing approach.
The same comment may apply to my open source projects - not sure.