The Marketplace is not open to 3rd parties at this time. Framework would like to open it up and are working towards this but it is not open yet.
As for the part, Nirav (Framework CEO) explicitly said “you can create your own hinge” so feel free to do so using any manufacturing method you choose, with a helpful hint that you may find custom tooling unaffordable. You can sell it anywhere you want at whatever price you want, but you can’t sell it on the Framework Marketplace yet.
This thread is getting a bit contentious so let’s leave it at that - you have your answer from the CEO himself, please go ahead and make the hinge any way you like and sell it anywhere you want at any price you want, just not on the Framework Marketplace at this time. No more arguing about this please or we will have to lock the thread.