Doesn't look open-source. If you are interested in having a Neon or git-like branching for PostgreSQL experience, have a look at Xata, which is based on ZFS like Delphix was:
There's no reason why it shouldn't, Delphix primarily targeted Oracle, but there is of course not as much open-source enthusiasm for supporting a proprietary database as an open-source one.
And also, of course, MS-SQL is only supported on Windows, and ZFS is not available on Windows. Windows does have Volume Shadow copy Services, but they are not as capable as ZFS snapshots and clones.