IVAO network has been using the Ivac ATC client and Ivap pilot client softwares for about 15 years if I remember well because I was joining the main developer of Ivap to an airshow in 2005.. and we were still testing the pushback feature to be included with Ivap.

It was already time for new generation softwares, and IVAO network is also willing to change the servers, which were at the beginning of this complete project.