> once a process is no longer bleeding edge, what's the benefit of keeping manufacturing details secret?
Even if it's not bleeding edge, there still might be special features or secrets they want to protect. For really old nodes, I think it boils down to two reasons: 1) Clients with money don't care about open design rules, so there was basically no demand for it. 2) Foundries generally have a pretty strong culture of secrecy, so without someone asking externally they're not going to open source anything.
assuming no one will invest the time and capital to build a similar foundry, is it fair to say that such secrecy has minimal benefits? or can an existing foundry learn these secrets and improve their own products pretty easily?
There's a lot of risk for new nodes and less for old ones. Exactly how much, I'm not sure.
I guess let me put it this way - I think it's entirely rational for them to be cautious. There's currently not a lot of upside to being more open, so it's usually not worth it even if the risk is small. Programs like this are great because they hit both sides of the equation: increasing demand for open PDKs while lowing the perceived risk by building a track record of successful releases.
Even if it's not bleeding edge, there still might be special features or secrets they want to protect. For really old nodes, I think it boils down to two reasons: 1) Clients with money don't care about open design rules, so there was basically no demand for it. 2) Foundries generally have a pretty strong culture of secrecy, so without someone asking externally they're not going to open source anything.