They claim to have wanted a tool that did this and nothing more. I'm guessing they realized if they did a little more work they could put it up for sale and ga

They claim to have wanted a tool that did this and nothing more. I'm guessing they realized if they did a little more work they could put it up for sale and gain another (mostly) passive income stream. Yes, it will do better than it would have otherwise due to their established audience. They're smart enough to leverage this to their benefit. Nobody is forced to buy it or even read about it beyond seeing a headline flying by. It seems consistent with the same strategy they applied successfully in the past to profit from Basecamp and Rails: both were leftovers or spinoffs of what was originally their core business, consulting. (shrug)