While custom software typically comes with guarantees (if it doesn't work, the provider is generally liable to fix it for free. If it's not "finished" on time,

While custom software typically comes with guarantees (if it doesn't work, the provider is generally liable to fix it for free. If it's not "finished" on time, it may even pay damages —determined by contract); shrink-wrap software (free or proprietary) generally comes with a nice piece of text saying that if it shreds your hard drive, or lag so much it makes you mad enough to throw yourself out the window, it's not their fault. Liability towards one customer is also not the same as liability towards thousands, or even millions of users.