Something is becoming pretty clear; if you want to run third-party software on your iPod touch, Apple’s going to ask you to pony up for that $20 software upgrade.

The software upgrade, for those of you that don’t have iPod touches, adds the payload of iPhone software. You know, the payload everyone has been complaining was missing from day one (Maps, Weather, Stocks, Mail, and Notes). But, it also adds WebClips and the ability to move items around on SpringBoard (the home screen). Oh, and it replaces the reflective dock with the aluminum dock from iPhone. The upgrade is free to new iPod touches, adding insult to injury.

But, here’s the newsflash you were waiting for… no upgrade, and no third-party software. Even if iTunes is used to deploy the payload, Apple won’t want you running third-party software with no way to manage the home screen. And, you can’t manage the home screen without the software upgrade.  The software upgrade has a lot of transactional code, and is actually both an enabler, as well as the first iPod touch/iPhone application to be released (it uses the same mechanism that iTunes will use to install third-party software on the devices).

Bottom line, no $20 upgrade, no third-party apps. And, with the number of iPod touches out there, that should be a nice padding for Apple’s wallet.