The link Sebastian gave is very interesting. It seems that the "rite" in question has very little known about it. I'm not finished with the review quite yet, but the author (of the review) doesn't presume to know the specific nature of the rite, only that it wasn't gay marriage. An excerpt:
Given the centrality of Boswell's "new" evidence, therefore, it is best to begin by describing his documents and their import. These documents are liturgies for an ecclesiastical ritual called adelphopoiesis or, in simple English, the "creation of a brother." Whatever these texts are, they are not texts for marriage ceremonies. Boswell's translation of their titles (akolouthia eis adelphopoiesin and parallels) as "The Order of Celebrating the Union of Two Men" or "Office for Same-Sex Union" is inaccurate. In the original, the titles say no such thing. And this sort of tendentious translation of the documents is found, alas, throughout the book. Thus the Greek words that Boswell translates as "be united together" in the third section of the document quoted above are, in fact, rather ordinary words that mean "become brothers" (adelphoi genesthai); and when they are translated in this more straightforward manner, they impart a quite different sense to the reader.
Whatever effect these liturgical ceremonials were intended to achieve, it is clear that they used ecclesiastical formalities to make two men "brothers," and employed various rituals and symbolic claims to confirm this relationship within the confines of the church.
Further, it would be interesting to note that the word which he is translating for love is
agape, which, anyone who has even a remote knowledge of Greek Philosophy knows is
not a romantic love, but Charity, or God's love (for humankind). It's a merciful and selfless love. An English translation of the rite in question which Boswell is (mis)construing as a gay marriage: (relevant Greek inserted back in)
In peace we beseech Thee, O Lord.
For heavenly peace, we beseech Thee, O Lord.
For the peace of the entire world, we beseech Thee, O Lord.
For this holy place, we beseech Thee, O Lord.
That these thy servants, N. and N., be
sanctified with thy spiritual benediction, we beseech Thee, O Lord.
That their love [agape] abide without offense or scandal all the days of
their lives, we beseech Thee, O Lord.
That they be granted all things needed for salvation and godly enjoyment
of life everlasting, we beseech Thee, O Lord.
That the Lord God grant unto them unashamed faithfulness [pistis] and
sincere love [agape anhypokritos], we beseech Thee, O Lord....
Have mercy on us, O God.
Even more interesting to note is that the priest requests from God that their love (
agape) "abide
without offense or scandal" which would be unnecessary if the early Church endorsed gay marriage.
Link to said review:
http://www.fordham.edu/halsall/pwh/bosrev-shaw.asp