Polyamory is a relationship where at least one partner has sexual love (eros for our Greek enthusiasts) for more than one person. There are many forms polyamory can take. There can be 3 lovers where all 3 are involved with each other, such as 1 man and 2 bisexual women. Or where 1 is involved with 2 only, such as the man involved with both women but the women don't have a sexual relationship with each other. These two examples can be expanded out to include any number of lovers, genders and sexual preferences; three is just an easy number to use as an example.
What are some of the first sources that record polyamorous relationships? Ironically in the scriptures of the Abrahamic religions which often condemn it today. The Jews have laws for polygamy in the Torah; the Christians have the same laws in the first 5 books of the Bible; the Muslims are instructed in the Quran to read and follow the Torah. Islam wouldn't even exist if Abraham hadn't been a polygamist because Mohammed is descended from Ishmael, Abraham's son through his second wife. (Abraham had 3 wives - see Genesis 16 and Genesis 25.) In Deuteronomy there are laws permitting polygamy, which is a marriage of a group of polyamorists. Some argue that those laws only exist in the Old Testament and are no longer valid because of Jesus in the New Testament. Hmmm. Matthew 5:17 "And Jesus said, "Do not think that I have come to abolish the Law (the Old Testament) or the Prophets; I have not come to abolish them but to fulfill them.""
Different polyamorous groups also define their relationships in different ways. Some believe having more than one lover without the knowledge of all the lovers is ok, while others believe everyone should know and be consenting. Integrity is unfortunately in short supply in our world today as is true love. We believe polyamory is perfectly acceptable as is monogamy. Some people wish to share their life with more than one lover, some do not. Either is perfectly acceptable. As consenting adults, the lovers are free to choose. There is no universal wrong done by loving more than one person; if there was no one could love their friends, family and lover(s) all at the same time.
However, what difference is there between cheating and polyamory if a person is in a monogamous relationship with someone and has a lover on the side? There isn't. Technically that's polyamory, but it's also cheating. The entire purpose of being a Professional Pagan is to dissolve the stereotypes of immorality, laziness and lawlessness that cling to the word "pagan". How can we conduct ourselves as professionals, be leaders and be role models if we aren't worthy of the trust of those we choose to share our lives with?
So how can people be polyamorous while maintaining morality and integrity? Simple: if everyone in the relationship agrees upon the boundaries which define the relationship, then it's not cheating. When there are no betrayals, lies or immorality, how could it be considered cheating? Whether a person chooses to be polyamorous or not is their choice to make, they can do it morally, and whether they are or are not doesn't determine if they're a "good" pagan.