"If redhat is gpl then why can't I download or obtain it for free? or am I missing something here."
You can download (and redistribute it!) for free - after You buy it. GPL does not mean "free as in beer". RedHat has every right to sell its Distro to You.
Under the GPL they have to give you the source code too, an You are free (as in freedom) to pass forward both the source and the binaries.
Intellectual property, trademark and so on, are not part of this.
By the same token, RedHat has no obligation whatsoever to keep publishing corrections to its Distro (barring maintenance contracts). They charge You for the privilege of downloading the upgrades - and these upgrades are under the GPL too.