Even if OSS isn't an option, I think it would be a nice idea for Light Table to provide low level API/Interface so that eco system grow like emacs/vim/eclipse.
Perhaps Chris has already considered this idea.
Yep, that should all be happening. Scroll to the FAQ section of the kickstarter - http://www.kickstarter.com/projects/ibdknox/light-table - it will be OSS and will also have an API for developing plugins with Javascript. He's already shown a cool benchmarking mode in one of the videos.