No, the GVWR is the weight the dolly can carry, including itself. GCWR is the combined tow weight, and I don't think FR specifies that (but you could ask). It is not usually given for a trailer.
The ball coupler on the tongue has a towing weight rating, though. The 2" coupler used on a FR dolly is typically rated at 5000 lbs. I see one FR model is listed as SAE Class 2, though, and that is only 3500 lbs, even though the coupler is a 2". I'd specify the larger model dolly (HDCD80SA) with SAE Class3 coupler (5000 lbs).
Car-Tow Car Dolly By Forest River
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL