There are three editions of LiteSpeed Web Server: Standard Edition, Enterprise Edition, and OpenLiteSpeed.
OpenLiteSpeed is open source. It is free to use, modify, and distribute through GPLv3 licensing. You can find download links and more information about OpenLiteSpeed at open.litespeedtech.com.
Standard and Enterprise Editions are proprietary software. Standard Edition is free for both personal and commercial use. The Enterprise Edition requires a license. Licenses can be purchased or leased in the Online Store. There you can find many different licenses to fit different server requirements.
Please see the Choosing A License entry for more information on different licenses.