Q. Can one eat apples with cedar/apple rust?
Cedar/apple rust is a fungus that requires a fungicide to manage and control it. Only a fungicide that is approved for edible fruit should be used, and that would need to be applied ahead of the harvest. When it should be applied, and at what rate depends on which fungicide you choose. Directions are usually supplied with the fungicide. I wouldn't eat the apples from the tree this year. However, if you can appropriately control the fungus next year, the apples should be edible.
Here is a link to a brochure from the Connectcut Agricultutal Experiment Station that should help you:
You might also want to check with the Montgomery County Extension Service which is located at 1015 Bridge Street, Suite H, Collegeville, PA 19426, 610-489-4315.