I believe so. The package descriptions for most of the ZFS packages in Ubuntu mention OpenZFS, so it certainly appears that way.
You can still create pools that are compatible with Oracle Solaris, you just have to set the pool version to 28 or older when you create it and obviously don’t update it. That will prevent you from using any of the newer features that have been added since the fork.
Well worse than that, Oracle closed sourced ZFS, so OpenZFS was forced to become a fork, and they are no longer compatible with each other.
As for GPL the CDDL license that ZFS uses made sure that code contributions attribute copyright to the project owners, which means they can change the license as they please without having to track down contributors.
You would think with their investments in Oracle Linux and btrfs they would welcome that license change, but apparently they need excuses to keep putting money into Solaris, and their Oracle ZFS appliances instead.
In any KDE app you can connect with SFTP in the open file dialog. Just type sftp://user@server/path and you can browse/open/edit files the remote server. ssh keys+agent make things a lot easier here obviously.