End note, moved to the top: My apologies if some of the material in this post is not within the bounds of traditional Christian or Jewish belief. It comes with the territory of reading and commenting on the Gospel of Judas. Yet if we're going to assess that document at all, then we go into that territory.
Anyone reading the Gospel of Judas will come across the names of spiritual beings such as Barbelo and Yaldabaoth, along with a cosmic origin story involving emanations / generations and aeons. These unfamiliar names are flags that the Gospel of Judas comes from a certain Gnostic sub-group called Sethians. Without claiming any familiarity with Sethians myself, I'll pass along that some encyclopedia references suggest that the Sethians were a fusion of diaspora Hellenistic Judaism and some Greek beliefs. This fusion could have been early enough to predate Christianity, though the available sources so far suggest that without confidence, as the early range of possible origin dates for the Sethian movement. At any rate, it would mean the Sethians could have been an existing group in the Jewish diaspora at the time the evangelists brought the news of Jesus to the Jews scattered around the Roman empire.
On the consideration that the Sethians may have already been in the Jewish diaspora when the evangelists began to proclaim Jesus, I'd expect that the Sethians were less-than-mainstream in the Jewish community. More than one line of reasoning suggests it. We're familiar with several Jewish sects from the Jewish homeland from that era such as Pharisees and Sadducees -- not so much the Sethians. Also, some of the key figures in their cosmology such as Barbelo are never named in the Jewish cosmology of Genesis, never mentioned in Jewish Scriptures, never discussed in the conversations about Jewish controversies that are recorded in the New Testament. If we were to make a Venn diagram of mainstream Second Temple Judaism and its belief systems, several of the Sethian tenets about God / divinity seem to lie squarely outside the area shared by Pharisees and Sadducees, though with enough overlap to see that the Sethians owe some of their views to Judaism (or possibly: try to incorporate their Jewish ideas of origins into their Sethian views).
The Sethian origin story (per the encyclopedia articles I've reviewed) has a sympathetic view of the serpent of Genesis and its role in humans' gain of knowledge, and possibly in humans' freedom from lesser religious systems. It is not a far reach to see a parallel with the Sethian Gospel of Judas and its sympathetic view of the betrayer's place in redemption. If the Sethians are as much about that alternative origin as the encyclopedia articles suggest, then the Gospel of Judas is a nearly-obvious interpretation of Jesus' betrayal from the Sethian point of view.
Why does this matter for us in our modern day? That depends on each person's interest in assessing the older texts that are presented as alternative gospels. I have mentioned before that I see some of these "alternative gospels" as coming from a stage in which the first Jewish-Christian evangelists met other cultures. While the New Testament shows us the Jewish disciples grappling with the Gentiles' non-Jewishness, it looks to me as though we see the opposite happening in some of the alternative gospels. We see non-Jewish cultures grapple with Jesus' Jewishness, or re-interpret Jesus within their own cultural and philosophical references.
Because I have not at this point made any study of Sethians for their own sake, my knowledge of them is limited. Their worldview in the Gospel of Judas -- with layers of different generations/emanations and their respective divine beings -- comes across to this novice as complicated, tedious, and contrived. My underlying interest is where this puzzle piece fits into the classical world's understanding of Jesus. With its reliance on figures such as Barbelo and Yaldabaoth, the puzzle piece fits outside of the area that is bounded by Jewish Scriptures or grounded in Jewish Scriptures, edging into the esoteric beliefs of some sects in the diaspora.