Licenses
Compiler
The FreeBASIC compiler (fbc) is released under the GPL license.
Libraries
With the exception of LibFFI (which is used for `ThreadCall`), 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 following license, found at https://github.com/freebasic/fbc/blob/master/src/gfxlib2/license.txt:

    libgfx2 - FreeBASIC's alternative gfx library
    Copyright (C) 2005 Angelo Mottola (a.mottola@libero.it)

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

    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.

LibFFI is released under the following license, found at http://github.com/atgreen/libffi/blob/master/LICENSE:

    libffi - Copyright (c) 1996-2011 Anthony Green, Red Hat, Inc and others.
    See source files for details.

    Permission is hereby granted, free of charge, to any person obtaining
    a copy of this software and associated documentation files (the
    ``Software''), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Documentation
The documentation is released under the GFDL license.