Much of plugin/reason.vim was copied from Vim-Plug, which is under MIT Just like vim-reason-loader is released under MIT. https://github.com/junegunn/vim-plug/blob/master/plug.vim
Much of the Reason syntax highlighting was coppied from the vim-rust plugin (see the comment header in after/syntax/reason.vim).
The vendor/ directory vendors dependencies on
vim-shell and
vim-misc but vim-reason had to include
them because it's difficult to load them from a vendored directory.
It shouldn't cause any problems if you already depend on those same plugins elsewhere