dhtmlxSlider is available in Standard Edition only - Download
You can use dhtmlxSlider for free under GNU General Public License v2, or Free License that allows you to use the component in a non-GPL application/website.
Open Source - GPL v2 - Allows you to use dhtmlxSlider in open source, GPL-ed projects for free.
Free License - Allows you to use dhtmlxSlider in non-GPL, proprietary projects (applications) at no charge.
dhtmlxSlider Standard Edition is distributed under GNU GPL v2 and Free license (details)