You don't upload entire 2-5gb iso or vm images to github or gitlab imo. The sorun.me project itself is in fact hosted on github - not sourceforge. Will admit I had no reason to be on sourceforge at all until I was like "Hey.. I need a place to host these images." and I realized that sourceforge is still a thing and perfect for hosting such large images for free.
Of course I could host it myself - but I guess I should just provide links on my actual sorun.me page.