Can we agree that OpenJDK is (…) open source (…)?

Yes.

Can we agree that OpenJDK is both open source and performant?

I can’t agree with something I don’t know enough about, and about what I have read opposite statements and experiences.

I have no doubt that in some context, OpenJDK could perform as well as OracleJDK. Some APIs and methods can have been well written from the start. What I do know about software engineering though is that Alpha and Beta stages exist for some reasons.

I haven’t seen one negative word about Swift.

Seek for the root of the thread.