Yeah, it's a perfectly fine place to land. My objection is completely to claiming to be 100% open source when it isn't; if they'd just said 99% open source, or that everything they'd written was now open, then I wouldn't mind (or at least, I'd view it as unfortunate, but I wouldn't be upset with them).
This is classic HN. At first infuriating if it corrects ME, and then amusing.