Do I need a commercial license for qt software?

I want to develop an Open source application (probably licensed with a MIT license), I would like to use Qt but I can't afford the commercial license of Qt right now. Do I need this license or can I use the Open Source license of Qt ? Thanks in advance !

Note that asking license-related questions is normally considered off-topic. In any case: the Qt commercial license is not required for releasing any Qt related software, and you have to buy one only if you don't want to (or can't) respect the open source obligations. Which means that if you release your software as open source you don't need the license. In case of PySide, you can also release it without the source code (since it's LGPL). In case of PyQt, you need to buy the PyQt license (which is not a Qt license) if you want to release it commercially and not publish the sources.