A little information on getmangos from vanilla-wow.wikia

[madmax]

Mangos / getMaNGOS

Mangos / getMaNGOS was the first widely used emulator for private World of Warcraft servers.

Started in Summer 2005 by TheLuda (Founder of Mangos) it has grown to become one of the biggest names in the wow server emulator community.

We are unique in that we are the only known project to have "test servers". These are not like traditional private servers - they are different in the fact that they are supported by our development team here at getMaNGOS. They are up 24x7x365 and are designed to act as closely as possible to the original Blizzard servers.

Players on the getMaNGOS test servers (Covenant-Wow.com) are able to report bugs directly to the getMaNGOS team to be fixed, allowing players to be directly involved in making the content as "Blizzlike" as possible for the test servers as well as others.

Because of getMaNGOS's open-source nature, all fixes / corrections are released into the main source repositories as soon as testing is complete. No Fees / charges are ever requested.

 

Most of this topic is taken from here and has been reworded or reformatted to be easier to read.