Hi David,
I totally agree with you. "I can think of no other explanation for why releasing 4+ years of effort has been almost completely ignored. If someone can point out why the open source community has ignored Supra Browser I would be all ears!" . My opinion is that the proponents of open source are a minority group of people. But they are loud. So, It feels like they are everywhere. Counting totally on open source community for traction is not a feasible idea. thats what i have learned so far. But one need to decide the business model beforehand. For few projects open source model will work. checkout Tonido ... it is very similar to Opera Unite. I will check out supra browser.