I'm not a fan of backing Kickstarters in general. I've been burned by vaporware too many times. I'd like to see the product fully designed, produced, and reviewed before considering it.
It's an interesting concept, but modularity in keyboards always seems to benefit the company, not the consumer. I think most people get a setup they like and leave it that. And meanwhile, to support the modularity, you have to deal with proprietary software (a red flag on a kickstarter), proprietary add-ons, a lack of repairability, and often compromised stability / points of failure.
That said, it's an interesting idea. I'd be curious to see it's final implementation, given it ever comes out.