You're well within reasonable bounds to request that they be removed or ask for an attribution. If you created those images, they are covered by copyright, and their use of those images without permission is a copyright violation.
I'm not familiar, but from a quick review it looks like Lloyd's algorithm is a few citations down the chain. I started from [1], which is based on [2], which uses Lloyd's algorithm (check out the Related Work section in the first paper).
Still, that's a good stand-alone link – I'll add it to the writeup.
Glad to hear it! FWIW, you are using Lloyd's algorithm and the first paper is too ([1] mentions Lloyd 7 times so it's unclear why they didn't put his paper in the references section, that seems like an oversight.)
Nothing wrong with using the Wikipedia article as an informal reference, but wherever you reference the other papers, considering linking to Lloyd's IEEE paper directly.
Splitting the centroid computation into a two-pass accumulation is a great idea. Even though that makes for heavy shaders, I imagine it's still faster than doing a buffer read and finding the centroids in one pass via CPU?
I'd also be interested in hearing how you decide on convergence. Are you stoppping after a fixed number of iterations? Or are you able to track the offsets using the GPU - not sure if that is possible since you're writing back into the VBO directly? You probably know from playing with it that Lloyd's algorithm is notorious for very long convergence times. It gets close very quickly, and then can have a super long tail with many small iterations and then sudden large changes long after it seemed like things had settled. It's super fun to watch, especially when you dynamically add points, very reminiscent of cell division -- you should make a video for your project page!
You might be interested in this paper too: http://www.dgp.toronto.edu/papers/ahausner_SIGGRAPH2001.pdf This one uses GPU Voronoi + Lloyd's algorithm to generate mosaic tilings. The neat trick here is to use a Manhattan distance instead of a Euclidean one, in order to get voronoi cells to line up in mostly rectangular grids instead of approximating a hexagonal packing.
Speaking of attribution, why doesn't that article reference Lloyd's algorithm? https://en.m.wikipedia.org/wiki/Lloyd%27s_algorithm