Are they part of the same company?

From my research, I would say yes. It looks like they even use both names on some products as if AccuCut is the original and they have branched out to AccuQuilt for a new target market--quilters. AccuCut seems to be aimed at teachers and scrapbookers. Such as, "Come see AccuCut's new AccuQuilt strip cutter."

Yes, they are the same parent company. The studio cutter and the grande cutter are the same unit. the accucraft dies will all work on your studio cutter. You can buy a platform on the accucraft side that will let you use Go! dies in the studio cutter. They have different 'accounts' so if you order from both sides on the same day, you get 2 separate bills. Ask me how I know this. The craft side seems to have more sales, just ending a 50% off sale yesterday. If you do applique and have a studio cutter, check out the shape dies on the craft side.