I read that Kendo UI Professional and Telerik UI for ASP.NET AJAX are included with Sitefinity licenses. Can I use these products for projects that are not related to Sitefinity?

No, you are not allowed to use the included additional Telerik products outside the scope of your Sitefinity projects. You can learn more about the licensing of the included developer tools. If you would like to use these products for other projects, you may purchase them separately.