After some extensive searching, I believe that they are called Servo Erector Set (SES) brackets, from Lynxmotion, although the article itself also uses the term servo brackets.
About the Servo Erector Set
Think of the Lynxmotion series of servo
brackets as an Erector Set for servos. These components are extremely
versatile, making virtually any mechanical arrangement possible. It's
now possible to build custom robots to your specifications! The
brackets are available in black anodized aluminum. The ball bearings
provide for precise low friction movement. The tubing, hubs and hub
connectors are precision fit and really expand what is possible to
build. They are made in the USA from high quality aluminum alloy. We
also have a series of laser cut Lexan chassis, torso, and electronics
carriers that truly complete the set.
If you want to build a variety of different robots using the SES
system, consider the complete SES V1.1 Construction Kit which contains
everything you need to get started.
The article also refers to them as Hitec servo brackets.
Hitec Servo Brackets
Our selection of standard brackets can use most standard size Hitec
analog or digital servos. The HS-3xx, 4xx, 5xx, 6xx, 54xx, 56xx, and
59xx servos are verified to fit. Note that servos from other
manufacturers are not guaranteed (nor likely) to work...
So, the term SES may only be referring to the kit of various Hitec servo brackets.
The first place that I saw the term SES, was on the page, WALKER8 – An Octopod Project, where it is mentioned in the comment:
I decided to go with the SES route
This may not be the most definitive answer, but it is the best that I could come up with. Maybe the answer is simply [Hitec] servo brackets, as the brackets were first designed to fit Hitec servos, and their derivatives.
Whether or not the brackets where designed by Hitec themselves, or some other third party is not clear.
If someone else knows, or has an idea of, a better answer, please post it.