(I am the author) Some of the use-cases of mojo I could think of:

1. Rollbacking DDL changes (like create table, adding columns, etc)

2. (My use-case) Multiple readers-single writer. Readers read old versions. Writers do not block readers and vice-versa. Note: this is different than reading+writing in the same version can still happen but with database-level locking.

3. Extension of #2: The older versions read from S3 so that lamda can read.

4. Extension of #3: Readers reading from old immutable snapshots makes the database as a queue of complex changes with indexes and all the benefits of SQL.

5. Backups and replication.

Oh: I have change the license to MIT