Comment by kfogel

It's not open source; the Hacker News headline is wrong. The Numworks web site does not claim it's open source, by the way -- the problem is only in the headline here. The license is Creative Commons Attribution-NonCommercial ShareAlike (CC-BY-NC-SA), and the presence of the "NonCommercial" clause makes it unambiguously non-open-source. If that clause were not present, CC-BY-SA would still be an odd license to use for software anyway, but because of the NC clause we never get to that issue.