I tried to set full permision on the list for the user and the button to edit Infopath is still grayed out. What permission should I set for the user so he can modify the infopath form on the list, and to crete new infopath list.
Set permission in site scope(for that user can access library):
site actions -> site permissions -> Grant Permission -> choice user and select only the permission "Contribute - Can view, add, update, and delete list items and documents."
Set permission in list(InfoPath):
Library Permissions -> add user with full control.
this permission allow the user create new form library, create content type InfoPath, deploy form in list, and edit form in list or contente type.
If your InfoPath have code and run in browser, unfortunate not will work because need Administrator approval.
hope this helps.