It could still be with AWS in mind. After this change, they'll be in a better negotiation position vs. AWS, since AWS can't (as easily) threaten that they'll build their own competing offer.
> AWS can't (as easily) threaten that they'll build their own competing offer
Elasticsearch changed their licence for more or less this reason [1]. So it wouldn't surprise me if Grafana's motivation was to solidify their position against Amazon.
> Elasticsearch changed their licence for more or less this reason
And look how it's going for them. AWS very nicely forked elsasticsearch and now has the fork that seems to be gathering quite a bit of momentum. I doubt that AWS was even considering talking with them after they announced the license change.
