I'd just like to interject for a moment. What you're referring to as DDNet, is in fact, DDmax/DDNet, or as I've recently taken to calling it, DDmax plus DDNet. DDNet is not a server unto itself, but rather another free component of a fully functioning server network made useful by the DDmax coremaps, chat utilities and vital system components comprising a full server as defined by Teeworlds.
Many DDNet players use a modified version of the DDmax server every day, without realizing it. Through a peculiar turn of events, the version of DDmax which is widely used today is often called "DDNet", and many of its users are not aware that it is basically the DDmax server, developed by Tsin.
There really is a DDNet, and these people are using it, but it is just a part of the system they use. DDNet is the team: the group that allocates the server's resources to the other servers that you run. The team is an essential part of a server network, but useless by itself; it can only function in the context of a complete server instance. DDmax is normally used in combination with the DDNet server network: the whole server network is basically DDmax with DDNet added, or DDmax/DDNet. All the so-called "DDNet" servers are really servers of DDmax/DDNet. (edited)