Sometimes a central authority is a good thing. But no-fucking-body is telling me what software I can or can't download, or banning me from downloading certain titles over some stupid shit like this. And this is just a mild example of what they *could* do if they wanted.
Well, the developer (ANY developer, mind you) can get sued for trademark infringement, so even your "open access" rules can get curtailed.
This much is true...
Yes, if you make a "memory" game, expect to receive some cease-and-desist soon, regardless if it's walled, garden, open-source, whatever.
And Apple has so far let users keep their "removed" apps. I think even iCloud keeps a copy if you happen to not have a backed up copy.
Nope, it's nothing to do with a walled garden (which actually doesn't affect users so much as developers since removed apps still can be used by existing uesrs). This affects *ALL* developers.
... but you're missing an important point. The significance of the "walled garden" reference is this: if I am a developer of an application that uses the word "memory" in its title or as a keyword, but in a non-infringing way (and it's hard to imagine that every single possible use of the word "memory" infringes the trademark), then outside a walled garden, I have options: I may choose to capitulate to avoid a lawsuit, or I can choose to take my chances with the legal system and continue using the term (and, if I can get a good lawyer, I may well win). But Apple is not giving developers that choice - they can either remove the term "memory", or remove the app entirely.
I suspect that Ravensburger have taken action to protect their trademark, and are only likely concerned about apps that are similar to / might be confused with their product - and Apple are indeed probably liable if they are selling infringing products. But, rather than vet individual apps based on whether they infringe or not (which is time-consuming and error-prone), Apple have taken a decision to impose a blanket ban on the term - which, while I see the practical benefits from their point of view, is clearly detrimental to, say, people searching for an application to check what DIMMs might be compatible with some hardware they need to upgrade...