It still is legally forkable, as much as it was before the change.

Oh, it will backslide. This won’t run on lastest Chrome in 10 years time.

It’s not open source and development has not stopped.

It’s always been closed to contributions.

It’s a client-side app, AGPL doesn’t work here.

It’s not open source, I’ve never called it open source, even before the license change. It’s a public source code project.

Nobody, but if it got to that point, that would be too late.