The term pagan seems to have come from the Latin root paganus, meaning anyone who isn't a Christian or a Jew. According to Webster's, the term was first applied to any or all of the polytheistic religions, particularly those of Greek and Roman origin. Interestingly, it is a term that was first apparently used by Christians to describe anyone not of their faith, but the term was not applied to Jews and Muslims because these faiths were monotheistic (they believe in only one god).
In more recent times the term pagan (and better called neo-paganism) has been adopted by some who have turned to what seems to be a pantheistic view of the godhead. The term pantheism was coined by an English deist J. Toland from the Greek roots pan (comprised of all), theo (god), and ism (doctrine). It is the theology that God is not a personality, but that all laws, forces, manifestations, etc. of the self-existing universe is God (Webster's). Neo-pagans, in their own new, self-definition, tend to be earth-centered and ecologically-minded. The term "live and let live" could easily be adopted as their mission statement. As a rule, they would like to be seen as gentle, kind, conservative (ecologically conserving natural resources), and tolerant/protectors of all life.
So, with that said, let's address Lauren's question of "Isn't being like Jesus a form of Paganism . . . where the belief and way to live is to 'do no harm to others'?"
The philosophy of "doing no harm to others" is very different from the teachings Jesus taught of "love God" and "love your neighbor." Doing no harm to another is a passive act while loving another is active. Indeed, Jesus told a story that lambasted those who did no harm, but did no good either (Luke 10.30-37). Jesus was very specific that those who chose to follow him were to be active in the world-and ecological conservation, or being kind to "mother earth," wasn't on his agenda, though appropriate stewardship of resources is a by-product of loving and honoring God. Jesus told his followers to get busy "making disciples, baptizing them, and teaching them to obey all of Jesus' commandments" (Matthew 28.19-20, para.).
Further, Jesus would have chaffed at any comparison of his teachings to neo-paganism. Jesus, if he was anything, was quite specific about naming God as a "personality." Jesus taught that God was the God who created the universe, not the God of and inextricably intermingled with (that is, a part of) the universe. Paul wrote "God gave them up . . . because they exchanged the truth about God for a lie and worshiped and served [creation] rather than the Creator . . . " (Romans 1.24-25).
Being gentle, kind, ecologically-minded, and tolerant/protectors of all life is a good thing, but it isn't the main thing. The main thing is to love God with all our hearts, minds, and souls and to love others. It's not enough to "do no harm," when there is so much good that must be done in the name of love and in the name of God. Neo-paganism emphasizes creation, not the creator, and it's "do no harm" just isn't enough. It won't do anyone any harm, but it won't do very many any good either.