I’d just like to interject for a moment. What you’re referring to as Linux, is in fact, GNU/Linux, or as I’ve recently taken to calling it, GNU plus Linux. Linux is not an operating system unto itself, but rather another free component of a fully functioning GNU system made useful by the GNU corelibs, shell utilities and vital system components comprising a full OS as defined by POSIX. Many computer users run a modified version of the GNU system every day, without realizing it.
Ready? GNU social is a social communication software used in federated social networks. It is widely supported and has a large userbase. It is already used by the Free Software Foundation, and Richard Stallman himself. If you would like to know how is it like to be a GSoC student at GNU social, read this blog post! Ideas Below is a list of ideas you can work on this summer at GNU social.