I had to look up what KDL is and what `Functional Source License, Version 1.1, ALv2 Future License` is.

So KDL is like another JSON or Yaml. FSL-1.1-ALv2 is an, almost but not really, open source license that after a 2 years becomes available under a real open source license. It's to prevent free loading from companies or something. Sounds fine to me actually.

Effectively, it's not meant to restrict people from using it, even in a commercial setting, just to protect my personal interests in what I want to do with it in a commercial setting.

KDL is more than just JSON or YAML. It's node based. It's output in libraries is effectively an AST and its use cases are open ended.