In this case, why not build a tractor from scratch? These guys have taken on the very admirable goal of building an opensource version of the most common of hardware (like real hardware, welders and cnc mills, etc) for the benefit of all of us. Opensource thrives on the fact that sharing knowledge isn’t zero sum. We all benefit much more from sharing than any one person loses by not keeping it to themselves. Upverter will always go out of our way to support the community in any way we can, be it homebrew cellphones, or tractors – so just let us know if we can help. And really, seriously, from all of us here – props. Way to fight the good fight.