As @DaveR believes, so it actually is! I checked your link, and it was last updated in September 2007 and says it’s compatible with SketchUp 6!
SketchUp has changed a lot since then, including significant changes in Ruby.
I think that expecting, even hoping, that it will work in SU 2017 is a forlorn hope.
Based on the description, perhaps @Medeek’s Truss Plugin/Extension can provide the functionality you need.