Moore's law is abt # of transistors, not density [1].
But I still see no reason open-sourcing would boost it. It's a capital-intensive process which is not where open source shines and is typically limited.
The reason is simple, even a single manufacturing fault can make a chip unusable. If you assume e.g. a fixed number of faults per wafer, you can easily see how increasing the chip area increases the area you have to throw away for every fault.
As you wrote, the semiconductor business is very capital intensive, so no one can afford to do that (except for some niche applications, like R&D, space, etc.).