From the user's perspective there is little difference. SaaS means you don't control the data or runtime. If others want to host Elastic as SaaS they just have

From the user's perspective there is little difference. SaaS means you don't control the data or runtime. If others want to host Elastic as SaaS they just have to negotiate a license. At least the authors of the software are supported. In this case the authors being supported by their ownership of SaaS rights are releasing the source to their product under terms that allow you to run it yourself for reasons other than providing it as SaaS. That means you can in fact control the runtime and the data if you want to do that. The alternative is to have someone else sell it as SaaS and not compensate the authors, running the risk that the open source will be abandoned. This is the SaaS equivalent of embrace-extend-extinguish.