[ghettoimp]

I'm a free software fan, but I don't see that open source matters here.

How do you know the machine is running the program whose source code you're looking at, instead of some other program that looks superficially like it?

If a machine produces convincing evidence of what it has done, e.g., a print-out that (1) the voter can meaningfully check before depositing, and that (2) is audited with at least spot checks or formal recounts later, why does it matter whether it is open or closed source?