> 100M lines of java code developed 'line-by-line'
If it's not generated, then it may be "versioned" that way. I saw projects where the entire codebase was copied over to new directories tens of times, and no previous "version" was ever deleted.
But, after giving it some thought, 100 mloc is really MUCH, like in 50x more than anything I directly worked with. It does sound kind of improbable, but hey, it could happen :)