This is an interesting window into their business model. This could be a purely an altruistic decision, which businesses sometimes do, contrary to popular belief. More likely it's a bet that wider adoption from making the clustered version free will drive more revenue through their managed database as a service offering. Which shows that their non-OSI open-source license is actually leading to more code and features…
Where "we" is defined as an extremely vocal minority on HN. I don't think most people take issue with licenses like this Timescale license or the BSL.