The Holy Kiss is probably "kissing on the mouth/lips"....
The Gospel of Philip says this :
"...It is from being promised to the heavenly place that man receives nourishment. [...] him from the mouth. And had the word gone out from that place, it would be nourished from the mouth and it would become perfect. For it is by a kiss that the perfect conceive and give birth. For this reason we also kiss one another. We receive conception from the grace which is in one another. ..."

What does this statement implicates why Jesus on the same gospel always kiss Mary Magdalene on the mouth which sparks jealousy among the disciples? Is his kiss a mere pure romantic acts toward Mary Magdalene? If it does,why does the disciples jealous?

"...And the companion of the [...] Mary Magdalene. [...] loved her more than all the disciples, and used to kiss her often on her mouth. The rest of the disciples [...]. They said to him "Why do you love her more than all of us?" The Savior answered and said to them,"Why do I not love you like her?..."

Kiss is an act of Love to someone.But on first quoted verse above it is more than Love,it says it is imparting Grace to someone aside from Love. However,giving Love is synonymous in Giving Grace. Thus,if Jesus always kiss Mary Magdalene on the mouth and the disciples become jealous of it,it only means his acts is not a mere romanticism toward Mary rather since he love her among the disciples he is imparting Grace symbolically to Mary....

However,there is another person Jesus was kissing on the mouth...that is the apostle James..

The Second Apocalypse of James : "...And he kissed my mouth. He took hold of me, saying, "My beloved! Behold, I shall reveal to you those things that (neither) the heavens nor their archons have known. Behold, I shall reveal to you those things that he did not know, he who boasted, "[...] there is no other except me. Am I not alive? Because I am a father, do I not have power for everything?" Behold, I shall reveal to you everything, my beloved. Understand and know them, that you may come forth just as I am. Behold, I shall reveal to you him who is hidden. But now, stretch out your hand. Now, take hold of me."

See on this gnostic scripture,it is not only Mary Magdalene whom Jesus kissed on the mouth but also the rest of his MALE disciples that is why the disciples were jealous..

No wonder,if apostle John whom he call himself "whom Jesus Loved"..perhaps Jesus kiss John also on the mouth....

This Male to Male kissing on the mouth or even only on the lips was demonized by the orthodox church today to be a "sinful kiss" because they have demonized "homosexuality"...But they are wrong..look what Jesus did.He himself kiss his fellow male disciples on the mouth and on the lips...is this homosexuality?