It's worth noting that Redhat's support of the rebuild distributions is entirely voluntary. If you buy a supported copy of RHEL they'll give you both the binaries and the source in one go, discharging their obligations under the GPL. Plus there's the large fraction of the distro that's not licensed under the GPL, and all the stuff Redhat owns the copyright on, none of which they need release source for at all, much less in nicely packaged, easily rebuilt src.rpms freely available to everyone online.
Redhat don't support the rebuilds because they have to, they do it because they want to. We can speculate on why that is, but my guess is that the reasons would include:
- No vendor lock in. It's a point made generally in favour of Free software, but it's particularly convincing for RHEL; if you don't like the support, stop using it, and run a clone. Other than the support nothing changes.
- Community relations. Acting like openness is something that you believe in, not something that has to be dragged from you is only good PR in a community like this, and it's this community that creates quite a lot of Redhat's product for them.
- Forming habits. If I need an 'enterprise' type distribution but I've got no money, or if I just want something to learn on, or I'm not sure it's the right way to go, I'm not going to stump up for either SLES or RHEL. I might try CentOS though, and if I do, then when I do need the paid support I'm going to go to Redhat because they support the system I'm already used to, unless there's a massively compelling reason to deal with the migration somewhere else.
I can't imagine why those reasons wouldn't apply equally to Novel, but maybe they can.