FOSS supporters always say this as if we live in a reality where knowledge and time are infinite. Yes, the licenses say you can legally do things, but they are hardly ever realistic.
Well, you don't do the maintenance yourself, you get some bored person to do it-- the important thing is they're not on a payroll and the result isn't someone's IP. Right now this strategy probably seems insane, because we are all so well compensated that the opportunity cost of working on OSS for free is massive, but sometimes you get 'lucky' and a software downturn frees up some engineering hours for further pro bono work on OSS. Pretty sure that has happened several times already, might happen again soon.
