I'm new to the Minecraft server world and I have a question: is it possible to let multiple users play on the same account on my Minecraft server?
You can never have more than one person using an account for multiplayer at a time, unless they are playing on different servers with at least one having authentication turned off.
If 2 players connect to the same server with the same name, the server will kick the first one to connect off.
TL;DR: Yes, but it's more work than it's worth.
If it's your server, it is possible to turn off authentication on the server (the call-home check) and not log into minecraft on the client, but everyone who doesn't log in will get the name "Player" - and guess what, there's only one "Player" allowed on the server - the second user will kick off the first, so, yay, you traded the usefulness of authentication for one extra user.
Turning off authentication also means you lose things like whitelisting; and you will need to find another way to control access to your server - say, a VPN, which is beyond the scope of this answer. IMO whitelisting is too useful, although I get that authentication it is effectively a rather nonintrusive DRM.
It is possible to write a proxy on the server that intercepts the login packet with the name "Player" and replaces it with, say, the hostname of the computer used (only really reliable on a LAN or VPN scenario; useless on internet at large where IP addresses change).
This was useful when the login servers would flake out in the 1.8/1.9 era; I could still play on the one private server on my friend's VPN. However, the login servers haven't been flaky for at least a few months, so I don't even know if it still works.
protected by Community♦ Jun 10 '12 at 12:36
Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.
Would you like to answer one of these unanswered questions instead?