The difference here is that the only schedule we're under is to have commits to the code base by the end of the semester. Though this is more structured than some guy's side project, it comes with the benefit of deliverables being a necessary part of passing the class.
Beyond that, in this particular case, we're talking about two individuals who've both kind of worked our way into code bases before. Specifically, we both made small patches for the Mozilla code-base as part of the pre-requisite course [1] and I've been doing some research coding that's involved a lot of reading and manipulating linux network internals; tools like LXR and MXR have been invaluable in getting there.
[1] Regarding the pre-requisite course, there's an open source project to be done every semester. Students work in groups of 2. Last semester, patches were made to Firefox, Chrome, Pidgin, FreeCol, Scala Testing Suite, and the Scala Eclipse plugin. I'd be happy to talk more about this if interested, but it was a really powerful thing when it came to learning how to get into a code base and write production code.