XAML Spy is commercial software. You can evaluate the fully functional product for 21 days. After the evaluation period you'll need to purchase a license, or continue to use XAML Spy Express, the free edition, with limited features. Once a license key has been purchased and entered, XAML Spy will work as a full version.
The latest releases of XAML Spy 1 and 2 are listed below. See the release notes for a complete list of all public releases of XAML Spy.