These are very good questions that you ask and I certainly don't want to sound like the last word on an area that comprises so much contention and variance. I do however know that the concepts that evolved over time with regard to Greek (hereafter Gk.=Greek) myths have been in fact highly "modernized" by which I mean they have been stylized to meet the needs of modern social constructs. This is in fact quite readliy demonstrable of many modern concepts, if we take for example, your own use of the term capitalism. There is quite a mythology surrounding IT and you know if you study it historically, that it has undergone quite an evolution as entertained by economists and mythologizers alike. Look at the way capitalism has been distorted by its enemies and supporters.
The idea of Gk love that I was referring to has a very elaborate background. I say that "romantic love" is certainly not a Gk concept. They had a concept called "hieros gamos", sacred marriage (whence our hierogomay). In mythology there are many examples of hieros gamos of which one in particular, the marriage of Zeus and Hera, demonstrates the union of CREATIVE PRINCIPLES. Hera is the protector of house and hearth (the primordial myth of the woman's place) while Zeus is the paterfamilias, in the sense that he is protector of something like an extended family. There is no reference here to "romantic love" in the modern sense. In the hieros gamos, the Gks celebrated a ritual in which a male and female principle would be chosen to represent this union of creative forces. It was (in modern parlance) a one night stand in which the community celebrated the principle of a sacred marriage. To mention "romantic love" in the context of Gk studies would be an anachronism. The foundations of Gk male/female unions are fertility, sexual compatibility, suitibility, and even economics (cf. Xenophon's ch. on "Vice" in Oeconomics). I would think emotion is somewhere in there but not the exclusive force.
In the fifth century, when much of Gk culture was unified, there was a great variety of forms (or what you referred to as forms)of love. Aristophanes poked fun at the idea of same sex unions. Why? Because Gk males could engage in the male/male act but, they were expected to reproduce. The union of two males in a relationship was not at all what we today would call a "gay relationship". It constituted a highly prevalent form of relationship, but it had MANY varieties. The concept of "Platonic love" is found in its philosophic form in Plato's "Symposium" and is deemed, in the end, the highest form of love by Plato. Again it was not a "romantic love" at all, it would be a misprision to even consider it in this light.
Also if you consider a society such as that of the Gks., it is so different from Christian (Northern European) society, that at times it hardly appears related. One of the central concepts that underlies "romantic love" is the presence of a SOUL, and perhaps even a concept of CONSCIOUSNESS (which possibly came into philosophy in the modern sense, through St. Augustine). Rand speaks of this in ITOE and was very reluctant to attribute it to previous history. I would think that a modern concept of consciousness would have some importance in "romantic love" of the Objectivist kind. Without a strictly circumscribed area of precise dilineation and concept formation you cannot come up with the concept of "romantic love" that Rand's philosophy promotes. In fact I would challenge anyone to even find an explicit treatment of same sex ROMANTIC LOVE anywhere in Rand's writings. We are treading on new ground when we speak of an Objectivist version of same sex romantic love.
In 1994, the late John Boswell, a scholar of same-sex unions in the ancient world attempted to show (Same-Sex Unions In Premodern Europe) that in the Middle Ages both Catholic and Eastern Orthodox churches sanctioned and sanctified same-sex unions. This is a very controversial topic. Camille Paglia criticized the study for reasons including Boswell's scholarly methods. It is very possible that some degree of Ancient Greek love and Christian notions of the union of souls was present in these same-sex marriages. Branden defines romantic love as "a passionate spiritual-emotional-sexual attachment between a man and a woman that reflects a high regard for the value of each other's person." But how can you have a concept of value without a concept of consciousness? By introducing "values", "mutual outlook", "sense of life", and "individualism" into the discourse, Branden moves away from the set notions of love in Western traditions. I think that there is some legitimate case for understanding adulterous relationships in his concept of romantic love because it is SO individualist. Would you call Romeo and Juliet individualists in the Objectivist sense?
Branden's book (The Psychology of Romantic Love, 1980) almost reads like an unspoken apology for adultery if you know the full context and then approach it from a traditional "romantic" point of view. I am almost tempted to say that Rand and Branden represented (for a brief period of time) the highest category of romantic love. HA imagine that! In my opinion Branden wrote a great apology (in the formal sense), but he should have reflected a great deal longer on what he meant by it. The enormous fluidity in his notion attempts to subsume the entire history of Western tradition WHEW. You can even see Gk concepts integrated into it, but who was Zeus and who was Hera? Rand may have played both roles at one time, as well as Branden. That is why I think that homosexual love or gay love COULD be included in Objectivism because it involves an enormous amount of CREATIVITY and a statement of INDIVIDUALISM vs TRADITION. Perhaps even an act of defiance ("coming out")In fact I think that Stonewall flows naturally from the tradition of LIBERTY. I view it as an evolution not a revolution. A series of events with contracts as well as some violence. As you will see I am very defiant and resist handing over GAY LIBERTY to Marxist Liberationists who want to appropriate GAY for the collectivist movement(s). They tend to see GAY exclusively as a revolution, or a series of acts of violence that ignores contractuality completely. You will see what I think of that in my forthcoming article on Richard Goldstein's "Attack Queers".
As far as casting modern gay relationships into a traditional concept of "romantic love" I agree with Speirs that it is far too constricting. "Romantic love" minus the heavy tradition, possibly. Joe, you and Derek are pushing ME in that direction:) I like the idea, but it has to be evolved carefully and consistently. Again I do not wish to appear as an authority on it (yet), and I know that it is a groundbreaking area of research. Five years ago could you have imagined an article like what Sciabarra wrote appearing in an Objectivist context? An installment? This site is exploring a new universe in my opinion. A giant step for mankind. I think I will write article on it. There are two levels in which this can be examined. First, it is important as you and Derek stress, to analyze same-sex, same-sex unions, gay relationships, etc. within the larger CONTEXT of human experience(s). Secondly, it is valid to isolate it scientifically (empirically if you like) in order to determine its constiuents or essential components. Please allow me your further thoughts and reflections, I value your ideas very much!