There's been a lot of righteous outrage about plagiarism in the poetry world of late. Rightly so: to take someone's work, change a few words and then pretend it's your own is an awful thing to do. Poets, of course, will continue to be influence by other writers and there's nothing wrong with that. Poets will borrow from each other freely, hopefully; but in their own words not the words of the borrowed.
Some have 'justified' their stealing as 'sampling' or 'collage'; and it's true that collage is almost the modernist technique par excellence, seen in the work of Pound and Eliot, for instance . The difference between Pound and Eliot and the average plagariser, however, is that both those poets were very open about what they were doing and they were creating entirely new works from collage, not pale imitations of the original texts, with just a few words change.
So I think, for those of us who do use collage extensively, it might be good to put down on this blog what are my personal 'rules of appropriation.'
1) It must be a completely new work Not an imitation; like a Yellow not a Red Wheelbarrow, but a completely new work. The notes at the back of the Wasteland tell you the sources he used, but they don't tell you anything about what the poem is about, because he is using the sources rather in the way Picasso uses collage: to make a new work.
2) Wherever possible, literary sources should be acknowledged, especially if the person sourced is alive; or pretty darned obvious if not. Not literary sources (I've used signage on shop windows for instance) need not be specifically sourced (in my case, I can't always remember which shop or advert I used) just generally acknowledged.
3) Tributes are ok as long as they're acknowledged. Centos: it would be better if the sources went with the poem, but if that proves awkward, then at least call it a cento.
4) I personally would never use the work of a living poet without their express permission. In the heady world of New York School poetry in the '60's, some poets, Ted Berrigan in particular, often recycled both his own and other peoples' lines; but he was part of a particular scene where that would probably be tolerated among themselves. And what he did with it was always new, often amusing and the original writer probably wouldn't have minded a bit.
5) Do not enter competitions. (That's a personal rule).
6) Make it new. Whatever else you do. If you can't manage that, take up painting by numbers or something.