AFAIK he does not owe his livelihood to anyone. He made his FU money from Tumblr, and a bit more from selling Instapaper, but since then his output (which, yes, has been iOS-focused) has been more like hobby projects that at worst keep him busy but at best may have made him a little extra on the side. The stuff he does now looks to me like someone following their bliss, not someone trying to make a living.
The way he talks on ATP, Overcast really is his primary source of income, and the Tumblr money is probably stashed away. If Overcast stopped making money, that would be a big deal for him.
