Neither is good nor evil. Both believe they are in the right and will do whatever it takes to make the universe as they see it. The Darkness believes the unuverse should be a hardcore version of survival of the fittest, the stron would survive but you would always have reason. The Traveler is moving towards a utopian universe, one where we all coexist peacefully but we essentially have no reason. Also, the Traveler causes the syzygy to eradicate all species on Fundament to prevent the spread of the Darkness. That's a very morally grey area. Not something you would expect from the "good" side.