License file versus wit.gemspec

[m-barthelemy]

https://github.com/wit-ai/wit-ruby/blob/main/wit.gemspec says this is a GPL-2.0 library, while the project's LICENSE.md is an unidentified but seemingly more permissive license.

We're trying to understand if this library could be included in a proprietary, SaaS product.
Would Wit be able to clarify the exact license of this Ruby client?