I assume you mean "take a penny" = "use the software for free" and "leave a penny" = "contribute back" (money or time).

With the plate there's a sign that says both "take" and "leave". In this case there is also a sign (the license) which only says "take". The intent is clear in both.

It's further not comparable because taking a literal penny deprives the next person of it, whereas here using the software for free costs the other users nothing.

But I'm not trying to nitpick the analogy, I only want to point out the the obligations (both social and contractual) are not the same, neither are the consequences.

Again, if he wanted to make money from his software, he should've put it in the license and charged the big users for it.