That depends on your use case, I just did a simple zpool with no redundancy because I wanted maximum speed/capacity and all my data is backed up on an external HDD. If you need redundancy, I would look online for how to configure that and what the optimal setup is.
No, it’s licensed under the LGPL, which means source code can be freely distributed and distros would continue to package it for free no matter how hard Redhat tried to paywall it.