As one of Vuo's developers, I work on Vuo's engine (the thing that makes compositions run), work on nodes, and write documentation. You'll see me on the forums answering people's questions about Vuo.
I've been developing apps and frameworks for several years (since I was in college). Pre-Vuo projects include Kineme Quartz Composer plugins, iOS apps for education, an app that analyzes photographs of tomato slices, and software to help people with disabilities use talking keyboards.
I enjoy using Vuo to make live music visuals. My hope for Vuo is that it will grow into a community of people of diverse backgrounds and identities making lots of different artistic, useful, unique, goofy, beautiful, crafty, wonderful compositions.
If running the composition with Vuo Editor instead of the command-line tools, there isn't currently a way to add a library search path. Instead, you should place the ARToolKit library in the User Modules or System Modules folder.
Oops, yeah, that documentation is wrong. Thanks for catching that, @unicode.
Could you describe how you intend to use the U/V expressions? Like, what is the task you're trying to accomplish, and how would the ability to manipulate UV texture coordinates independently make it possible / easier than just using X/Y/Z expressions? I ask because a concrete example helps when thinking about possible improvements to nodes.