How does this compare to a traditional ORM? I looked through the slides and the paper and this seems to largely provide the same kind of functionality as a regular ORM but with the caveat that you can only do key/value transactions.
For example if you read an object, read some fields, follow a reference to another object, loop over a list you find there, then make some changes and commit, the underlying transaction will only apply if those operations are conflict free.
However if we are to jump on in JDK world, persistence is not hard. Java have supurb db like H2 with full postgres compliance, that can be embedded in memory.
H2 is a cute database, but it doesn't even come close to having "full postgres compliance". Besides, it solves a completely different problem from Permazen or JPA - it's a storage engine, not a storage abstraction layer.