Short answer: One Muse invite code works for about 20–30 people. The exact cap can vary, and the number shown in the Muse app is final. Every one of those people gets the same reward: 1 billion tokens for redeeming, and 1 billion tokens to the code's owner per redemption.
Per code: about 20–30 successful redemptions, then the code is full. Per account: one redemption, ever — no account can redeem a second code, even a different one. The first limit is about sharing; the second is about claiming.
A full code simply stops working for new redeemers. Nothing is taken away from people who already redeemed it. If the code you tried is full, use any other valid code — the reward is identical. The pool on this site (claim a free code) serves codes that still have room, and codes reported full are retired.
Every successful redemption of your code earns you 1 billion tokens, so a code shared with 20–30 new users earns its owner 20–30 billion tokens in total. That is why owners share codes publicly — and why this pool exists. You can submit your own code on the home page.
Q: How many people can use one Muse invite code? A: About 20–30 people. The exact number can vary; the count shown in the Muse app is final.
Q: Can I redeem more than one invite code on my account? A: No. Each account can redeem one invite code, ever, regardless of which code it is.
Q: What happens when a code is full? A: It can no longer be redeemed by new users. People who already redeemed it keep their reward, and any other valid code gives new users the same 1 billion tokens.
Q: Do I earn tokens when people redeem my code? A: Yes — 1 billion tokens per successful redemption, so a fully filled code earns its owner roughly 20–30 billion tokens in total.