&gt; Would it be possible (read: legal) for someone to modify the ZFS source to be more easily buildable into the Linux kernel, but then distribute it as source code only<p>Yes and that has been done. The ZFS on Linux[0] distributes a DKMS source package that each user of ZoL uses to build a binary kernel module. DKMS automatically builds the module without manual interaction from the user, similarly to installing a regular binary package.<p>This is legal but the resulting kernel&#x2F;zfs module is non-redistributable.<p>[0] <a href="http:&#x2F;&#x2F;zfsonlinux.org&#x2F;" rel="nofollow">http:&#x2F;&#x2F;zfsonlinux.org&#x2F;</a>