I used FreeCad a few months ago for the early prototype you can see in the video at www.flair.zone.

It doesn't support assemblies yet (although its on a branch!) so I just designed a linkage system extremely carefully and swiss cheesed some parts to avoid dealing with dimensions as much as i could. I used to use Inventor but Fusion 360 is nice - and its free for startups.

As soon as Freecad supports assemblies I will probably switch back. I hate booting into OSX for Cad work and back home to linux for coding.