I remember around a quarter century ago, I'd jokingly tell folks how software prices could be significantly reduced by having "sponsorship" where a portion of the screen/time would be allocated to advertisers. The standard mode would often interrupt you in the middle to show an advert ("we interrupt your regular application for a special message from our sponsors..."). The alternative was the "PBS mode" where most of the time you're get free uninterrupted use the software -- except for those times when you struck those "pledge break" periods lasting the entire day, where it would get longer interruptions in the normal usage and play a guilt-trip on you for not having contributed...