I am a religious person, but I follow my heart and do what's right for me. I've had friends who were very very religious. I respected them and would tone down my usual antics. The way we behave around home is not always how we can behave around our friends. At home, often we curse a bit, even around our kids. I'd rather them hear these words at home and know not to repeat them then learning them from others. When I'm around others, I don't curse and respect that different houses use different words.
If you want to remain friends I think maybe it might be wise to have a conversation with your friend. Let them know you respect their beliefs and their choices and they are not for you. I would ask that if anything you say or do around them is offensive to their beliefs, that they kindly let you know and maybe explain why. Then when you're hanging out in the future you can avoid that and not offend them. It works both ways. If you don't like talking about a certain subject etc. let your friend know. In order to maintain our friendships, we need to be open, honest, understanding and respectful. We are all different and unique and that's a good thing.
My religious friends, didn't appreciate the fact that I didn't accept their religion as mine and did not want to completely change my beliefs. We stopped talking, her kids never came over to play with mine or help babysit anymore. The saddest part about it is my girls lost a few friends. But that's the way things go sometimes. People change and they do grow apart. Do what feels right for you.