[1]Granted, I'm thinking of European definitions here, because I get really confused when I try to educate myself about American ones. An GmbH is more or less an AG with stakes rather than shares, whereas an American LLCs seem to behave somewhat differently (taxation, for example is pass-trough).
It's not really a union of assets nor people though. The former would be a trust or arguably a non-profit, and the later would be a partnership. And LLCs can elect to be taxed as a C corporation, although I can't fathom why one would. (And most small businesses can elect pass-through taxation!)
I also would not refer to an LLC as a collection of assets for a common purpose; instead I would say it is a popular entity form that limits member or manager liability. However you could take a different view.
And I can't imagine a restaurant could work the same way as Valve. In a restaurant, you have to feed people day in day out. You can't deliver a Michelin-quality meal when the inspiration hits you and nothing when it doesn't.
Valve also seems to have a strangely forgiving customer base. I don't think I've ever seen anyone complain about micro-transactions in their games, whereas other publishers seem to get a lot of hate for it. (Then again, ever since I stopped playing games, I've began to notice that each publisher had their own unique method of fleecing their customer base, so it may be that Valve got the players that tolerate micro-transactions, whereas others would have the ones who tolerate endless DLCs.)