Yeah sure, if I'm a huge enterprise and I want to run something like elasticsearch in house, I have 2 choices:
1. Get elasticsearch delivered as an inscrutable binary blob
2. Get elasticsearch delivered as binary blob but with its source as well so that I can see what ES is doing underneath the hood.
In most cases of proprietary software, the big clients eventually in case #1, do end up getting the source of the proprietary software as well. Just that the source is for viewing only not for modification.
What ES did was better than that, they made source available to anyone (including the small fish). This doesn't weaken the need for ES to make money through selling their sofware, just that the purpose of releasing the source is more towards "viewing" it and less towards making modifications and reselling it.
But confusingly sort of being open source is only going to create pain in the long run.