Unfortunately this is standard for TUM's database group. Their previous database, HyPer was similarly cutting-edge, but was closed source under a proprietary license. Last I heard it got sold to Tableau.
And Hyper is alive and well at Salesforce/Tableau! The team working on it is still in large parts the original Hyper team from TUM. You can actually download Hyper (as a binary with language bindings) and play around with it [2] for non-commercial use cases.
If you think Hyper/Umbra is cool, the TUM database group has lots of other very interesting projects going on at the moment. LingoDB [3] pushes the database-as-a-compiler idea to the extreme by implementing query optimization and compilation query compilation in MLIR. LingoDB is open-source. Also Viktor Leis, who stands behind (among many other things) Hyper's Morsel scheduling and ART indexes as well as Umbra's buffer management recently started a very interesting project [4] to heavily co-design the DBMS together with the OS in a unikernel approach. Really interesting stuff!
