: For instance, when I bought my plans they state that
: I have the right to build one kayak.

That, of course, is why many people choose to start with free designs
and modify them to suit themselves. Anything I design or any designs
I modify, I republish in the same spirit as open source software ... I
use one of the Creative Commons licences for just about everything on
my website (usually CC-BY-SA-NC). But for those who make a living out
of their designs, we need to respect their intellectual property.

Andy