The problem with extracting org-mode into its own application is that a lot of the magic of org-mode comes from emacs. It's not so much being tied up in emacs as sharing and extending the design. By moving org-mode elsewhere, you'd reinvent the wheel and put an artificial division where there doesn't need to be one.

For example, org-babel allows you easy access to any language you have support for in emacs. Same syntax highlighting, same behaviour, same utilities. Improve any of that and org-mode takes advantage of it for basically zero cost.