Believe it or not, the Gospel of Judas, the Gospel of Thomas, and all sorts of alternative Gospels have been around for a very long time. Regardless of the fact that we have only been recently aware of them doesn’t make them go away. The reason these works did not make their way into the Bible is actually quite simple. They are works associated with a competing body of faith to Christianity.
Many people, especially modern scholars, would like to equate Gnosticism with Christianity. Gnosticism can be viewed as a form of monotheism, but that pretty much is where the similarity ends. Even though many Gnostic works do refer to Jesus or God, by and large, they are based on a completely different theology.
It would be interesting if all that Gnostic work from the early days of the Christian Church were consistent, or if they actually had a workable set of doctrines that would spell out a fairly clear set of parameters for a workable theology. Unfortunately, none of these statements are true. In fact, Gnosticism was spread throughout the ancient world precisely because every person is their own Bible. Every person is their own interpreter of divine truth, their own prophet, or priestess in front of God.
They believe that God dwells in all people, and people can have a direct, intimate and unique experience of the divine existing in everyone. This sounds great in theory, but the problem is the practice. There were so many inconsistencies with Gnosticism that it was easy for the early church fathers to look at the total body of Christian work.
They looked at all the epistles written both by Paul and other authors, as well as early stories regarding Jesus, which later on coalesced into the four Gospels, and clearly saw that these texts were so different from Gnostic texts. The difference was so stark that it’s actually fairly easy to filter them. Keep in mind that there was a tremendous amount of confusion because there was the 3rd letter to the Corinthians, the 3rd letter of Peter, all sorts of Gospels. It turns out that a lot of these were just really Gnostic texts relabeled as traditional Christian texts.
The answer to the question: What is the impact on the Bible? The big impact was that it pushed the early church to focus on textual continuity by actually doing deep level analysis of all the scripts that it had access to. Then, a pattern emerged. In fact, this pattern is fairly easy to spot.
Real Christian texts talk about the centrality of a saving relationship between God and man. On the other hand, Gnostic texts are just all over the place. There was no central organizing theme, and it was very easy for the early church editors to filter them out.
That ultimately is the main impact of Gnosticism on the Christian Bible. If anything, it pushed the early church to get serious about clearly identifying which Christian or so-called Christian texts are truly canonical and which ones are simply immaterial.