[tonfa]

The numbers for the kernel are well known (and they are hard to beat for any open source projects): https://lwn.net/Articles/395961/ (for every version ~1.1k devs and around 10k changesets)

[jgesture]

Indeed. I don't recall the exact numbers, though I've heard both Linux and RoR numbers, I think that Linux has factors more developers committing to it than RoR.

Linux is, perhaps, the most rapidly changing piece of software in existence