Yeah, that sucked for sure and we hated to disappoint people like that (co-founder here). But you have it exactly backwards. FoundationDB was never open source. There was a binary that you could download and use as a trial, or you could buy a license for real use. The users that bought licenses got to keep using those licenses. Some of those customers went on to build billion-dollar businesses on top of FoundationDB (Snowflake!) A few years after acquiring the tech Apple themselves open sourced it (!) so now it is open source. The big challenge for users is that most of the sophisticated "layers" that make the tech into more of an easy-to-use database rather than just a storage engine are still proprietary.
Yea it was over 8 years ago, I didn't work on the team so I don't remember all the details - I just remember this decision impacted them hugely. Hopefully it worked out well for you, but the decision - weeks from their launch - impacted their mental health, as well as the project.
