This old plugin was written prior to SU2013, the
SketchupExtension class and it’s easily installable RBZ archives, and the establishment of the Extension Warehouse.
So it was written for old Ruby 1.8.x, it has some old versions of Ruby Standard Libraries enclosed as well as some gems, but is also trying to load RubyGems itself and then install other gems. In addition it’s files have non-standard indentation and incorrect module encapsulation (for a shared environment like SketchUp’s) making an overhaul time consuming.
And so it cannot benefit from Ruby 2.x, it’s Standard Library and RubyGems being distributed with SU2014 and higher. (Ruby 2.x is when Unicode string and path support begins for SketchUp on the Windows platform.)
Basically, it is a large complicated codebase that would be a major overhaul job.