So, I'm not versed enough in legal matters to be certain about this, so I tend to fallback to caution, but (A) customers I've worked with in the past seem to be wary of such copyleft licenses and (B) the contagious nature of such license would make me think twice about using it in a project of my own as well.

It would be nice to have such notion challenged but I'm not sure what would change my mind.

I would expect that most commercial companies that use Grafana would obtain a commercial license?