Unfortunately, this completely depends on what terms-of-service are provided by someone whose parts you use in the game.So if someone makes a non-commercial game and later on makes a commercial game, but uses the non-commercial game to grow success on the commercial one, would that be considered using the product commercially?
I wouldn't think so...
Commercial or non-commercial are simply facts choosen by most people to use and make a difference in their terms-of-service, but basically you have to abide by all regulations set into the terms-of-service of those pictures, scripts, sounds, whatever you want to use in your game.
If someone puts into the ToS that anyone using his sounds needs to have the game's title screen based on the color yellow and call the main actor YXCDERGF, then you would have to follow those conditions if you want to use the sounds.
That is an extreme example, but unless a specific licencing option is overrule by courts as violating basic rights, then anything might asked in the ToS - no game developer is required to use the resources offered in the package, but if he does he has to obey every rule in the ToS.
Most people are only interested in the difference between commercial and non-commercial use, but I know of one ToS that specifically states that putting up a donation button for the free game is concidered commercial use by that person.
