Is it considered a duplicate submission if I make the submission from a different source?

That isn't a decision for us to make, but instead, we let our
users determine that aspect of duplicate submissions. A submission is considered a duplicate if made in the same format and related to the exact originating URL link. However, we strongly discourage submitting duplicates as this steals credit from the first submitter and if caught abusively duplicating submissions, this could lead to your account being banned.