Accepting money from willing customers, who are paying you for access to some technology you created that they find valuable, is not theft. Quite the opposite, it's almost always two happy parties engaging in an exchange that each of them finds advantageous.

I don't think most people would use this definition. It covers gambling/lottery winnings, finding buried treasure or a gold mine, and paying someone to file your taxes and splitting the extra deductions they found. Really, it includes employment at large- the only 'non-theft' employment would be that which provides no net benefit to the employer. There are parlances where these are included intentionally and they share a starting syllable, but to the common people this is not a definition of theft.

Everything is a rich man’s trick.

- Documentary