CentOS

Will a Dell Optiplex 960 run Centos 5.8?

5.8 is years old and unsupported.. The current version is 5.11.
Version 5 is in last stages of support, so you would be better off running V6.6 or V7.

I understand. However the application I need to run is limited to 5.8. The author cautions running anything later or problems may arise.

Will the Optiplex 960 run with 5.8?

I believe so. But there is only one way to be absolutely sure . . .

The author cautions running anything later or problems may arise.

Sounds like excuses for bad code to me.