> And for the posts on social sites, are they more often about the creator or what they created?

You hit the nail right on the head. Github is about sharing code. The code is the creation. Github's unique selling point is the webinterface to show the code: It's the best designed interface in the industry to show code in a browser.

> Does GitHub provide this feature better than SourceForge or others?

Various software is available to show code in the browser, but none works as well and is polished as well as Github. The creation (code) therefore can be best shared on Github. As such, others willing to check out the creation are, from the moment they arive at github, mostly busy this exactly that: check out the creation (code). Every time I visit repo's visualizing the code in html on other places then github, I get agitated by the annoying interface. Example: some interfaces require you to click on a file, after which the postback returns a site containing a list of revisions, and new buttons to 'view' a revision. This causes me to wait for a postback, and click, twice per file I want to view. Github instead instantly shows the last revision.

All these small tweaks account for much better usability on Github compared to other sites.

I guess for scientists, there must be the same approach as Github approaches programmers. For programmers, it's about code, and for scientists, it's about data and the conclusions derived from it. Instead of showing code, show a paper with the possibility to drill down on data. The data being shared can then be treated the same as code being in a source repo, so the usual git stuff (branching, merging, pulling, pushing) can be applied on the paper+data.