Disentangling source packages vs. binary packages vs. support contracts
Greg's original post had claimed that RHEL "requires a subscription to the closed source Red Hat Network update system". Nope. For reasons cited, this is not true: You can get the full distribution at any time in source RPM format (including the two slightly proprietary non-software packages), without any subscription at all. It's on the public ftp site. You can also get the distribution in built binary format (but with substitutes for RH's trademarked logos and artwork) from CentOS and others.
As to one's ability to "get support without RHN": That's something different. Red Hat ties its support contracts to RHN -- but (avoidable) support contracts have nothing to do with whether software is open source or not.
One might ask: Is it lawful to get a copy of the RHEL binary packages as built by Red Hat, Inc. (e.g., copies of the RHEL binary ISOs)? As mentioned, the source packages from which those get build include two trademark-encumbered non-software packages. The process of compiling the binary RPMs puts some of the trademark-encumbered logos and images into sundry binary RPMs thus built. So, some subsets of the full binary RPMs set would be subject to trademark-based restriction, e.g., against _commercial_ redistribution that arguably could create brand confusion. This is probably the biggest reason why, in practice, it's very rare to find RHEL binary ISOs, along with the fact that the publisher would be underwriting huge bandwidth bills without the legal right to charge for access -- and the fact that it make more sense for people wanting RHEL without a support contract to just fetch CentOS.
That aside, to the best of my knowledge, it would be lawful. But nothing requires that anyone offer it to you, just as nothing requires that support be offered a la carte on term to your liking