Early in the development of iLand (around 2008/2009) we were looking for a technical platform that we'd build upon. Based on previous experiences, we decided on C++ as the primary development language very early, which limited the our options quite a bit.
We selected Qt as our main toolkit for the following reasons:

• it is an open source framework much used in the open source world
• allows cross-platform development
• comes with a broad range of built-in functionalities (from accessing files to multi-threading)
• is big enough so we could expect a long life of the project

In hindsight (as in 2016), selecting Qt prooved to be a good choice. Qt is still being actively developed and new versions come out regularly.