Why do you think the Zapcc developers would have worked for free on this? It seems pretty clear that they developed the software because they thought they coul

Why do you think the Zapcc developers would have worked for free on this? It seems pretty clear that they developed the software because they thought they could make some money off it. And thanks to the fact that they did this, we now know it is possible. Competition will hopefully motivate the Clang developers to develop similar performance improvements in the mainline of Clang. Everyone will benefit. A Clang user is certainly no worse off than they were yesterday.