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Hmm, OK..
But I think Firebase is one of Open Sorce Software according to https://www.firebase.com/terms/oss.html and https://opensource.googleblog.com/2017/05/open-sourcing-firebase-sdks.html.
Thank you for your review, but I hope you consider this again.

Hello,

Firebase itself is not open source.

Open-sourced parts are client libraries and SDKS which is built for Firebase consumers. (It's mentioned exactly like that in the URLS you have sent.)