[richardfontana]

Recent versions of RHEL actually include a GPLv2-oriented written offer for source, but this is in addition to Red Hat simultaneously making corresponding source available along with binaries (for all packages regardless of license).

[bonzini]

But is it valid for any third party, i.e. does it allow a Red Hat customer to use 3c?

[richardfontana]

It's explicitly valid for any third party. I would assume that a customer could use it even where (as should normally be the case) the customer would have source code access under 3a.

There are a lot of drawbacks to use of the written offer option so I'm not sure if Red Hat will continue to use it with RHEL in the future.