Well, if you still have 50BTC you want to throw at it I have a couple of layout guys who will moonlight doing it. Do the first tapeout at MOSIS, then buy a mask set once it's verified. At that point, if you want to open source the GDS you're free to do so.
It would take a lot more than that. Form a 501(c), build a project and test plan and publish a budget. Identify a qualified team that's committed to moving forward if the needed resources are available, and the key milestones where funds are needed.
With that it really wouldn't be hard to raise the funds. Whether it's via angel investors for a start up, or a kickstarter approach with a public domain solution as the end point would be up to you.