Yes, gmg dotproof can be SWOP 3, 5 or GRACoL certified. I'll do it all the time.
Well, colorproof cannot print dotproofs (halftone proofs) only contone proofs.
To print a dotproof you will need "dotproof option" for colorproof, which changes the software name to "gmg dotproof" instead of gmg colorproof.
Now, dotproof CAN print dotproofs (halftone screened proofs) AND colorproofs (contone proofs). GMG is the best of the best. Find a dealer and ask for a demo. You can also send images to gmg website, they will make proofs for you.
Check this link:
Welcome
I am using gmg with Hp Z2100 and many Epsons 98x0 series.