Unfortunately it must work because people keep doing it. If it didn't increase revenue companies would stop doing it.
It's the same with those timed modal windows on blogs. They piss a lot of people off. But they also increase email capture rates, and sites with large audiences usually see revenue increase as a result.
If SourceForge want to stay afloat, they should reinvent themselves as a decent GitHub alternative or pivot. Bundling malware for kickbacks and keeping the old site design won't take them anywhere good.
It's the same with those timed modal windows on blogs. They piss a lot of people off. But they also increase email capture rates, and sites with large audiences usually see revenue increase as a result.