That's wrong: they pay Grafana Labs to use it as proprietary, as noted in another comment:

https://lwn.net/Articles/1019686/#CommAnchor1019710

> Grafana's a great example of this. AWS and Azure _could_ have sold the unmodified AGPL Grafana as a service or published their modified versions, but instead, they both struck proprietary licensing and co-marketing agreements with Grafana Labs.