I don't think this is possible unless you jailbreak the device.
This is basically what the suggestion you mentioned means.
Jailbreaking the iPod. Then you can install software from any source.
Cydia
http://cydia.saurik.com/ is a directory of applications for iDevices that you can install on a jailbroken iPod/iPad/iPhone.
There is also an application available with that name that allows you to install these apps directly from the device