Steps I took that resulted in the problem:
It just freezes on startup.
Install was a bit weird: after mounting install image normally, copying to Applications took ~10 minutes. After all, it’s just 334MB…
I tried to download and install it twice.
What I expected should have happened instead:
My version of Fritzing and my operating system:
0.9.3b, El Capitan 10.11.5 (15F34)
PS The same version starts normally on my 10.10.4 (14E46) Yosemite.