The gospel of Philip does say something like this, although Brown (or, more precisely, his sources) apparently has access to manuscripts that scholars have never seen if he knows where exactly Jesus is said to have kissed Mary Magdalene. Only one copy of the gospel of Philip survives, and this copy is damaged. The word indicating where Jesus often kissed Mary Magdalene is missing as a result of this damage, as are some other words. Most responsible translations then present this verse in the following fashion: “And the companion of the S[avior . . .] Mary Magdalene [ . . . loved] her more than [all] the disciples [and used to] kiss her [often] on her [ . . . ]” (GPhilip 63:34). Brown and his predecessors essentially have to supply the word “mouth” in order to guarantee that people will draw the desired conclusion, namely that the verse suggests a romantic/sexual relationship between the two. The word “head” or “forehead” would obviously not carry the same connotation, although one can easily imagine some other words that would carry an even more sexual connotation as well. In other words, the verse does not conclusively state one way or the other the nature of Jesus’ relationship with Mary Magdalene; one would need evidence from elsewhere to draw any kind of definitive conclusion. Such evidence is lacking, however. Indeed, even if Jesus did kiss Mary Magdalene on the mouth, this would not necessarily imply a sexual connotation.
The best scholarly discussion of this passage in the Gospel of Philip is by Antti Marjanen. He points out that kissing can have both sexual and non-sexual implications, but there are several reasons why the sexual interpretation of kissing is not very likely in the context of the Gospel of Philip. “First, in the only other passage [in the Gospel of Philip, which would be the best indication of how the author understands the significance of kissing] where kissing is referred to (58,30-59,6) it is used without concrete sexual implications as a metaphor of spiritual nourishment which leads to spiritual procreation. Second, in other contemporary religious writings there are plenty of examples where kissing functions as a metaphor for transmitting a special spiritual power. . . . Third, the altercation between the disciples and the Savior in Gos. Phil. 63,37-64,9 suggests that kissing is not to be understood as an expression of sexual love” (The Woman Jesus Loved: Mary Magdalene in the Nag Hammadi Library and Related Documents, 158-159). To restate this last point, a “sexual” interpretation of the kissing of Mary Magdalene would require us to believe that the jealous disciples are expressing their desire that Jesus would kiss them on the mouth rather than Mary Magdalene. Marjanen continues, “Fourth, in 2 Apoc. Jas. 56,14-1, which is the most interesting parallel to Gos. Phil. 63,34-37, it is said that when the risen Lord wanted to reveal his most secret mysteries to James he kissed him and called him his beloved. In that context it is fully clear that kissing has no sexual connotation. It is a symbolic act that demonstrates James’ privileged position.”
I should point out further that kissing, even between a man and a woman, did not always have erotic implications in the ancient world, especially in the context of Judaism and Christianity. Kisses could indicate kinship and were also used as an outward sign of reconciliation. The apostle Paul enjoins Christians on numerous occasions (e.g. 1 Thess. 5:6) to “greet one another with a holy kiss,” and there are instances of this where it is clear that the addressees would be kissing members of the opposite sex as well as of the same sex (Romans 16:16).
Finally, the author of the Gospel of Philip, like many other Gnostics, seems to be an advocate of what is called encratism, which involves a rejection of marriage, procreation, and sexual activity of any sort. It is the ultimate irony that Brown is trying to rescue a healthy, positive view of human sexuality (a project that I heartily endorse) but does so by misreading a text that does just the opposite.