The FreeBASIC compiler (fbc) is released under the GPL license.

The runtime library (libfb) is released under the LGPL license, for both the single-threaded and multi-threaded versions, with this extension to allow linking to it statically:

"As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version."

The Gfx library (libfbgfx) is released under the LGPL license (???) http://www.freebasic.net/forum/viewtopic.php?t=17962

The documentation is released under the GFDL license.