Is there any one who can explain the support issues between a licensed product and a open source product which is a "built" of a licensed product?
Scientific Linux is a rebuild of RHEL (permitted by the RHEL license).
Updates are received via the SL channel.
Fermilab, the makers of SL, does not offer support to the general public. Clearly Red Hat doesn't offer support neither as it's a rebuild of their code. However, you can get some support from the SL community as SL is a community-driven project (like CentOS).