What is freeCAD? It's a parametric CAD software meaning that each step in your design process is “recorded” in a history. Thus the result of your design is not set in stone, but you can go back in history and change some parameters to modify the design, e.g. to adapt it to a new servo or change the length of a tigh / shin.
A second important aspect for choosing freeCAD is, well because it's free and open source. The intention of Kayra is to bring robotics, a little humanoid robot, 3D design, goal-directed 3D printing, mechanics, motors and software to all maker spaces and schools around the world. Thus, the software should be free of commercial interest. Luckily, we found freeCAD that has all the features that we need for Kayra.
https://www.youtube.com/watch?v=6JOITgw_T1Y
https://www.youtube.com/watch?v=cJfbINgyz-k