The primary license is MIT (see LICENSE.md). Note that this repository and the extension binary package also contain third-party sources, namely:
syntaxes/review.tmLanguage is taken from yanzm/ReVIEW, Apache License Version 2.0
review.js, packaged in the binary distribution of this extension, is taken from vvakame/review.js, MIT License.
and all the subsequent dependencies are packaged in the extension too.
https://github.com/erukiti/ya-language-review also provides Re:VIEW preview and diagnostic features. It runs review locally (while my extension is based on review.js) so you can get the very latest features, in case you need them.