If the Patent is still applicable Spyderco will go by the book and pay.
If the Patenet is not applicable Spyderco do not even have to give credit, but yet they do. Thus the Sage line.
Patents axpire after 14 years unless the original one is improved upon by the original maker and therefore is extended another 14 years with a new patent number.
Note: different continenets outside USA do not have to give credit to the original patent holder unless international trade agreements have stipulated such agreement.