From what I remember, the patent expired, but Spyderco had the round Hole trademarked, so legally you need their permission to use a round hole as an opening device. I believe for custom makers, Spyderco will license you for either $25 or $50, I think it is a one time fee, and then you can use it forever. There are makers who use holes, and are not licensed by Spyderco, Technically that is illegal, and If Spyderco wanted they could probably take legal action. As far as I know they don't bother with it. I am not suggesting that you not pay the fee, If I could make folders, I would pay them. They are a great company, and the price is very reasonable. They don't seem to really be trying to make money off the license fee. I believe Spyderco also does some advertising for makers who are licensed to use the hole, I believe they are listed on the Spyderco Website.
Kyle Fuglesten