> when the founder receives pay for their work, in the form of cash or exercised options or whatever else.

No. Earned income is salary, and taxed as such. Unearned income is capital gains, exercised options, etc, not taxed as income. It's pretty easy.

If we just use this tax office definition, it's effectively impossible to earn a billion dollars because you'd need to pay yourself ~$1.6 billion dollars in salary (depending on where you live), and very, very, few people can afford to do that