Since its listed on LFSWorld, its registered properly with the master server, so this tells us your server can talk to the outside world.
However, since people can't find it in-game, or connect to it from outside your network, we can deduce that people cannot connect in - usually this is caused by firewalls or NAT.
If you directly connect to the internet, unblock the incoming ports you've set LFS to use (by default TCP/63392, UDP/63392) in your firewall.
If you connect to the internet via a router, you'll need to port forward the ports to your PC. Take a look at portforward.com for information.
You may also want to take a look at this thread (
http://www.lfsforum.net/showthread.php?t=9572), as it contains information for common firewalls, amongst other nuggets of info.