My understanding is that Apple PCC will not open source the entire server stack. I might be wrong. So far I haven't seen them mention reproducible builds anywhe

My understanding is that Apple PCC will not open source the entire server stack. I might be wrong. So far I haven't seen them mention reproducible builds anywhere, but I haven't read much of what they just published. One of the projects I'm working on however intends to enable just that. See system-transparency.org for more. There's also glasklarteknik.se.