Medusa is a headless API, so you are free to consume it from wherever you want whether it be a React-based storefront, a C# backend, or something third - there's really no limitations.
But the source code of the open-source project is written in Node.js, so if you looking to contribute, you are forced to write JS.
Don't hesitate to reach out. We are amid extending our B2B capabilities, so it would be super interesting to learn about your client's requirements. And your own.
But the source code of the open-source project is written in Node.js, so if you looking to contribute, you are forced to write JS.
Re SDKs, there's an official JS SDK and a community-led Flutter SDK - that I know of. The former can be found in the GitHub repository here: https://github.com/medusajs/medusa/tree/master/packages/medu...
Disclaimer, I am co-author of the project.