A spectacular view of the entire Milky Way... using open source!
Well, not just open-source software: he needed a lot of processing power too, though nothing beyond a beefed-up home computer (it ran Linux, of course). And then there was the problem of actually stitching it together, and making sure every star and and entity in the visible cosmos looks correct, relative to everything else in the sky -- for that, he used catalogs of star data and sky background data from Pioneer 10 and 11. For the entire creative process, and a list of the programs he used, check out the creator's site.
The final image, which you can probably obtain if you're a student, and if ask the creator Axel Mellinger nicely, clocks in at an impressive 650 megapixels and 7.7 gigabytes.
But the best bit, which I dutifully saved until last, is that you can surf around the maximum-resolution image using another open-source application called IIPImage. Enjoy!