No, you’ll get different content based on everything from flaky federation (software that isn’t perfect) to differences in moderation.
So, for moderation, let’s do an example. Bob has an account on Server A. He posts a comment on a community with his Server A account which is federated from Server B.
But Bob breaks the terms of service / moderation rules on Server B. Server B mods block his account and his comment is not visible there.
If Alice views the comments on the post on Server A, she’ll see Bob’s comment. On Server B, where Bob is blocked, Alice won’t see Bob’s comment.
On Mastodon, servers will sometimes connect to Relays which specialize in moving content between many different servers, which is different than moderation blocks ;)
There are a number of licenses that do this. And yes, many of them are not OSI approved and people will say mean things about not using the word open source. Which you should ignore and instead perhaps say fair source instead if you care.
A couple to look at:
Big Time License
Prosperity License
I also recommend going through the back log of posts by Kyle Mitchell, an engineer - lawyer who has authored a number of great software licenses, including the two I listed.