Comment by CalChris

A lot of us learned this way from John Lions' Unix Commentary. There have been similar books for Linux and Apache. (They didn't have a concordance for the Linux Core Kernel Commentary so I wrote one and sent it the author who mentioned it in the second printing.) But I think for OpenBSD something like SourceGraph is more than enough.

I would recommend the SourceGraph people post browsers for Linux, L4, Xen, LLVM, ... and other great open source infrastructure projects. You'll drive more interest in your product in a helpful way.