This is not an open source license and it's untrue to say it's an open source project when it's licensed this way.
"IF ANY LITIGATION IS INSTITUTED AGAINST SUPABASE, INC. BY A LICENSEE OF THIS SOFTWARE, THEN THE LICENSE GRANTED TO SAID LICENSEE SHALL TERMINATE AS OF THE DATE SUCH LITIGATION IS FILED."
This is a poison pill. At best the licensing is naive and blocks even customers of Supabase from using OrioleDB, at worst it's an attempt for Supabase to provide themselves unlimited indemnity through the guise of a community project. It means the moment you sue Supabase for anything. Contract dispute, IP, employment, unrelated tort you lose the license. They could lose your data and if you try do anything about it they can immediately counter sue for a license violation. Using the brand of the postgres license to slip this in is pretty wild.
OrioleDB looks like a promising project and undoubtedly an great contribution from Supabase but it's not open source or really usable by anyone with this license.