A person of faith can embrace Naturalistic Humanism without committing heresy. It helps if the Supreme Being they imagine is both kind, gentle, and being omniscient, can recognize that humans are only the proximate cause of their behaviors, resulting in it also being non-judgmental and non-blaming. If one is a believer, envisioning such a supreme being is not inconsistent with a Naturalistic Humanism practice.
Believers considering involvement with Naturalistic Humanism should be aware that that in every religion the rules, laws, and customs are only the product of mere mortal men. If the laws and customs of religion were truly from a supreme being they certainly would not differ as they do. Even within religions much blood has been shed over sectarian conflicts, let alone the blood shed between religions in holy wars. Religious laws and customs are the product of mortal men who lacked access to the valuable knowledge that modern science and social science make available to us today.
Belief in a god, or in an afterlife need not be bundled to religious laws and customs that were invented by men and changed when it suited their needs. Believers can still keep what they consider most important, whether it be their relationship to god, or their faith that they and a lost loved one will, one day be reunited. Naturalistic Humanist can be added to any designation someone considers themselves to be i.e.: an Naturalistic Humanist Christian, Jew, Moslem, Hindu, etc.