You can't really compete on licensed league IP, since you'd need to acquire the license, and leagues want money.

"open source" doesn't really make sense for trading cards either, since the entire point is collectibility. It's not even clear what "open source" would entail at all.

Hell, even for a trading card game what "open source" means isn't really clear: you can already create your own format if you want, you're never going to be able to play bespoke cards at sanctioned events (way too easy to abuse), would it just give you the right to "fork" the TCG and reuse as many of the existing cards & rules as you want ignoring the rest?

That hardly seems useful as you can more or less already do that, everybody understands that an MTG ETB and a Hearthstone Battlecry are the same thing, you just can't use the exact same names (let alone reuse art because that is under separate licensing).

No: open source works because the economy of manufacturing software is so wierd. you can breakdown total costs into development, manufacturing, distribution. Software manufacturing and distribution cost are about as close to zero as you can get. So all it takes is one altruistic soul willing to shoulder the research cost. and there is no reoccurring manufacturing or distribution cost to burden this person. physical trading cards would have a recurring manufacturing and distribution costs. This is, strictly speaking, orthogonal to opensource, an open source trading card by definition would come with the design file used to make the card. I guess you could print your own cards.

No: the trading card appeal is scarcity of resource. there is no thrill of acquisition when you can get anything at will.

Yes: go to wikipedia and look up information of your favorite sports figures. feel free to put it in a nice template. there is your open source trading card.

Yes, but you won't like the answer. It's NFT-s. You need artificial scarcity in the digital domain for an economy to function so that trading and collecting makes sense.

   npm i football-trading-cards

doesn't really cut it.

It's been a while since I was a kid, but I remember collecting car cards from gums. I was the happiest when I had something rare others didn't. Same thing with a local Magic the Gathering clone, we went nuts with it and when someone printed a card it was really frowned upon.

Couldn't really make it collectible in the traditional sense, but an open source deck building game could be interesting.

I guess you could introduce collectibility by allowing artists to make limited runs of cards with alternative art.