Won't the results of this just be heavily biased via sampling by the fact that only certain types of people want to download and vote using an open-source public/private key voting simulation app?
Well, I think it's unfortunate that all opinion polls work that way. A small sample size can skew results in one direction. The objective is to get to a sample size as large as possible. I hope this goes in that direction.
No, most opinion polls don't work that way. Typically polls a) try and sample at random rather than self-selection and b) ask demographic questions that allows sampling to be adjusted to ensure it is representative.