Hi,
I would really like to be able to generate my own Guitar chord library , using my own voicings and fingerings etc.
Can anyone recommend an mac 0sx 10.5.8 compatable app that will allow me to generate my own chord diagrams please ? .

Take a look at Guitar Pro, it's really for tablature but it can create chord diagrams. You may be able to use it for your own application.

I Love it for transcribing Jazz chord solos.

http://www.guitar-pro.com/en/index.php