It's possible that I'm misunderstanding Sourceforge's goals, but for a site that is ostensibly about hosting software development, having the developer-oriented part of the experience be less convenient than that of an end-user seems backwards. I'm ashamed to say that I've never had anything on either Github or Sourceforge, but Github seems to be very much about sharing the sources, whereas Sourceforge seems to be much more about conveniently distributing the project's binaries.
This is probably largely related to the behavior of their users, though: Github's interface is not a lot more informative than Sourceforge's if no one writes a useful readme, and there have frequently been well-written projects hosted on Sourceforge that have lots of good information on how it works, or how to use it. However, I rarely seem to hear about new projects at Sourceforge, and frequently do see stuff at Github that has well-written introductory documentation accompanying the sources.
I frequently want to read about projects that solve interesting problems, but might not have the interest in installing or using it. Moreover, many people seem to now be using Github as a "Host my interesting document easily" host, which reinforces the "I go to Github to read code / read about code" perception. I'm sure a large part of it is confirmation bias, since most of the interesting code-related things I read about here are hosted at Github. ;)
Yes, it is very user orientated. Offering users free software with access to sources for those which are interested. And well, for a lot of software that just makes sense. Maybe not for the kernel or for web-development, but a lot for typical desktop software. SF isn't just about source-hosting, it's about hosting complete projects including distribution of binary packages, allowing that projects use custom homepages (instead of scary source-browsing...) and even support for user (and developer) forums.
I don't think it's that hard to see that this is still preferable for many projects.
It's definitely worse for reading through complete project code. For reading a single-file it's one click more than github which I can live with. It's very nice for getting a quick view on file-based changes, why and when someone did them and I use that interface a lot for that. I find it way easier figuring out file changes there than in github. SF is generally a lot slower (sometimes so horrible slow that browsing is near impossible). GitHub on the other hand sometimes freezes my browser when it has a lot of syntax highlighting to do (not sure if it still does, been a few months since I last run into that).
They have different ways to present code with different design targets and different problems. I prefer GitHub for reading code online without having to check-out, I prefer SF when already working with a project where I have the code locally and using the online interface to hunt for changes.
This is probably largely related to the behavior of their users, though: Github's interface is not a lot more informative than Sourceforge's if no one writes a useful readme, and there have frequently been well-written projects hosted on Sourceforge that have lots of good information on how it works, or how to use it. However, I rarely seem to hear about new projects at Sourceforge, and frequently do see stuff at Github that has well-written introductory documentation accompanying the sources.
I frequently want to read about projects that solve interesting problems, but might not have the interest in installing or using it. Moreover, many people seem to now be using Github as a "Host my interesting document easily" host, which reinforces the "I go to Github to read code / read about code" perception. I'm sure a large part of it is confirmation bias, since most of the interesting code-related things I read about here are hosted at Github. ;)