You can't really be sure about that, after all, his employees could promptly retire now that they're rich. (Though, this seems very unlikely)
$125,000 is a decent bit of cash, but it's not enough to retire on, especially after taxes.
that depends completely on where do you live. here in eastern europe it'd be _almost_ enough if you had nothing to start with and was smart about handling it.
in the us, that's 3 years of entry-level salary in software development...
In Argentina you could buy a house near the capital for about half of that, and the rest would pay frugal-ish expenses for several years. Not enough to retire on, but plenty of runway for the next project.