Old Flex version in FC5?

Hello, I use Fedora Core 5 to test Mobile IPv6 on Linux. In a recent version of the mobility daemon source code a change made to a lex file make the build failson FC5. This changes introduced some flex options to reduce warnings output during compilation. To my surprise these options are not supported by the current flex version shipped with FC5. I found it strange because FC5 is very recent. Then, googling a bit, I discovered that flex state seems a bit confusing: - Fedora ships 2.5.4a (released in 1997) - Gentoo has 2.5.33 - Debian has two different packages flex-old (2.5.4a) and flex (2.5.33) My question is: why does Fedora ships flex 2.5.4a and not a more recent one? What are the mysteries behind flex versioning? Thanks, Benjamin