"The short story is that Spyderco and Benchmade reached an agreement." - Sal Glesser, 04 Feb 2017
"When the patent was still in force, the shape of the hole didn't matter. We patented "hole openers". We licensed any custom maker interested but they couldn't use the design in production.
After the patent ran out, we trademarked the round hole shape since we'd been using the same shape for almost 20 years. Now we license custom makers to use the round hole which has become the "Spyderco look"." - Sal Glesser, 07 Apr 2005.
It appears from reading things written by others that Benchmade used the trademarked round hole without permission. I've never seen where either company has said what agreement was reached, and how.