I get what you mean and probably there are people like that, but I consider it mostly an exaggeration. Simply - the GPL has some clauses enforcing some obligat

I get what you mean and probably there are people like that, but I consider it mostly an exaggeration. Simply - the GPL has some clauses enforcing some obligations (to prevent some rights from being taken away from you, the end user - according to their wording, and I agree), these and other clauses make it legally incompatible with the inclusion of ZFS (CDDL license) in the Linux kernel (GPL). You can build it yourself (so indeed as a user you get to not care or obey) but not distribute it (this is the problem of your distribution's maintainer). Canonical's lawyers think this is not a problem if the ZFS code is distributed as a module, instead of compiled into the kernel itself, and since 2016 Ubuntu shipped with ZFS support. The BSD license is considered perfectly compatible with the inclusion of CDDL licensed code and therefore many BSD distros ship with ZFS (and Dtrace) out of the box without legal worries. Indeed Oracle hasn't come knocking. TL;DR: it's not a vibe. Some licenses are compatible with each other, some aren't. It also depends on how different licenses come into play into a "finished product" (e.g. kernel module vs monolithic build)