Doudna
explains what he means by "John of Ephesus":
In currently prevailing scholarly view the Gospel of Mark, with its Josephus-like John the Baptist, predates 93 CE in composition and is the evidence that the Josephus JB reflects Christian tradition. However that dating of the Gospel of Mark, however commonly understood, never was securely established as distinguished from hypothesized and is not stronger than argument from plausibility (as you recognize). The alternative argument is that the Gospel of Mark is later than and draws from Antiquities as a literary source for its John the Baptist material. But if there is no certainty of a pre-93 CE Gospel of Mark, and if John the Baptist in the Gospel of Mark is well explained as created from use of Antiquities as a literary source, what evidence is there of the Josephus JB figure current in Christian circles prior to when the Gospel of Mark was written? Paul’s letters do not know of a Josephus John the Baptist. Acts has a reference to “disciples of John” in Ephesus, also to an Apollos from Alexandria in Ephesus who is a Jesus-Christian who knows “the baptism of John”, but (a) Luke-Acts is second-century CE and Acts is widely understood to be filled with anachronisms and tendentious story-telling; but even more to the point, (b) is the John of the “baptism of John” of Ephesus, implied to be an adversary of Paul according to both Acts and Rev 2-3, the Josephus JB, or is it the Johannine John figure of Asia Minor associated with the Johannine writings of the New Testament known to Papias? I say the latter.
In this light there is no evidence the JB figure in Antiquities had anything to do with anything Christian at the time it was written.
Doudna talks of rivalry between John and Paul in Acts. But this rivalry doesn't say the identity of the Paul who is meant: the Catholic Paul or the marcionite Paul?
The connection with Apollos/Apelles makes it slightly more probable that the original Johannine John was in the marcionite camp, since Apelles himself was a disciple of Marcion.
(In addition, the Pentecoste episode in Acts is based on the descent of spirit on the followers of the "baptism of John").
Then his name and legacy were both catholicized by before connecting his name with the Jewish Book of Revelation and after by catholicizing his epistles and the Fourth Gospel.
Note
en passant that for Earl Doherty the
"Jesus masked as angel of light" (cursed by Paul) was the same Jesus hallucinated by
Apollos. Not coincidentially,
Apelles also talked about a Jesus of light who masked continually himself during his descent in the lower heavens.
Stantibus sic rebus, the enigma of John in the Fourth Gospel is sufficiently resolved.
Where I am less persuaded is about the authenticity of the Baptist passage in Josephus.