If you learn poses off other people's art, then you copy their mistakes, so it is better to get a real life or photograph version. I have seen poses created with a 3D program, and a lot of artist uses them. It is www.posemaniacs.com
The 3D version looks good, but it is actually wrong in a few areas, because of the 3D model was created to bend, and that is not the same natural way it looks. It is a good place to get started, and if you look for how they are different than real life people, you can learn the right way, but the first thing you need is to learn from one source, because you can learn from many different people posing.
It's just a pose. You could fine it anywhere, or have someone pose for you. I'm no expert, but I'm pretty sure a pose can't be copyrighted. Also, they're just drawings. You can draw an OC or a non-OC- nobody can keep you from drawing what you want. Hope it helps!