Answer : CentOS 5's EOL is Q1 of 2014 (though maintenance updates are for a couple of years more). Hence we do not think that making the script compatible with CentOs 5 is benefiaical for anyone on a long run.
Again, if you wish to install FFmpeg using our script, then you will need to have :
a. Python version 2.6 or above.
b. automake 1.9 or later instead of 1.14 which comes with CentOS5
c. autoconf 2.69 or later
In case you want us to manually install FFmpeg on your CentOs5 server, please open a ticket with us and we will be happy to help.
PS : Standard installation charges of 20 USD / hour will apply.