Mod Server listed on Non-Mod Server

Hi, i saw some server have mods on it ( like Pippi, Vanguard, etc ). But it listed on Non-Mod server ( without check on show Mod Server box )
I really wanna know how to do that, i just want to add Pippi on my Dedicated Server. But it required ppl to check on the Show Mod Server Box to see my Server.
Would be very grateful if someone knew about this and helped me !