Not really in anyway, they are freeware.

OpenRA might be GPL, but that's a complete re-implementation and extension of the original engine.

I'm not talking about OpenRA, but the source released by Electronic Arts under GPLv3 with the Remastered Collection: https://github.com/electronicarts/CnC_Remastered_Collection

It doesn't include the full engine, but as far as I'm aware this is the full source for parts specific to Red Alert and Tiberian Dawn, as the main motivation for releasing the source was to facilitate modding. I haven't looked very deep though, so do correct me if I'm wrong.