Looks like it is an overlay for volume.

Got it! Thanks for pointing it out to me.

Hmm. This client doesn’t seem to have that option.

Open source is an industry term, the code is NOT open, it's available. I can read it. I cannot use it in anything that might net some profit in the future. "open-source" is defined by the OSI here: https://opensource.org/osd/.

To be fair to OP, they didn't say open source until their response to your comment. They just said source code released for non-profit use. You are correct, though, that this is not open source.