All butter comes from cows when it's real butter so all butter from cows is good for you in moderation but since the butter including grass fed butter is high in fat it can cause weight gain as well as heart problems.
But grass fed butter is a healthier option when it comes to butter since grass fed butter is rich in omega-3s, CLA, beta-carotene, antioxidants, and vitamins A, K, D & E.
Grass Fed Butter that comes from Grass Fed Cows vs grain fed cows also has 5 times more conjugated linoleic acid (CLA) than butter that comes from grain fed cows.
So that does make grass fed butter or butter that comes from grass fed cows a healthier alternative to other butters but still eating too much of any butter is not healthy.
So eat it in moderation and you'll be just fine.