The problem is that almost all of the parties you mention (clients, relays, media servers) are running at a loss, at least without grant funding in the picture.

A good client takes at least one dev to maintain, and that's one dev's fair compensation, with some clients running full teams and a hefty amount of in-house infra on top.

Many relays are running at a pure loss, when you look at infra costs, as well as spam and CSAM mitigation etc. If you add at the cost of incorporation and licensing, which are being almost completely ignored by multiple parts of the system, this only adds to the list.

So in the end what can end up being the censor is simple economic reality. If grant funding stops tomorrow then economics steps in and says "you play by my rules now".

ActivityPub is different because it can actually run on its own financial steam. BitTorrent as well, it has the financials worked out. But Nostr is still at very high risk of being censored by nothing more than the need for humans to pay rent every month.