Free WebSite Or One Individu Company (known as Single user license)
If you're using iSynch for your personal usage, Education, your personal company (aka you're the only one in your company) you can register your version using this license. If your company counts more people than just you, you can't use this license.
More than One Individu in the Company (WebSite without paid advertising) (known as Site license)
If you're using iSynch for a commercial Web site (which doesn't contain paid advertising) or for your company which counts more people than just you, you can register your version using this license.
Commercial WebSite (With paid advertising) (known as Worldwide license)
If you're using iSynch for a commercial Web site (which contains paid advertising), you can register your version using this license.
Remember, you buy a license to use iSynch or iSynch Lite, but not iSynch nor iSynch Lite.
6.1 Enter the key
To display the register dialog to enter the key, click on the Register button in the 'miscellany' panel from the Preference dialog (Edit menu).