SourceForge's reputation has been on the decline since it became apparent it was wrapping installers hosted on the site with rather unwelcome adware. GIMP was one of the first to part ways with the FOSS repository and over the last few years, other prominent projects have also given the site the flick.
As gHack's Martin Brinkmann writes, not long ago, SourceForge started commandeering popular abandoned pages and adding something extra to the installers. SourceForge was found out and stopped the exercise, but the damage was already done. Along with GIMP, VLC kicked the site to the curb a while back, but now NotePad++ has also joined the no-SF club.
SourceForge already had trouble on its hands with the rise of GitHub and other online repositories and these recent departures are certainly not going to help.