If you only count each version once then do you only count official releases or do you increase the count by 500MB when someone corrects a one character typo in their copy of the linux kernel source on their laptop hard drive?
How do you count the size of the git repositories that can check out a million different versions but only store the differences?
I think I have some very old CD-ROMs of compressed debian source code, does the compressed or uncompressed size count?