Julia is licensed under the MIT License:

> Copyright (c) 2009-2012: Jeff Bezanson, Stefan Karpinski, Viral B. Shah, 
> and other contributors:
> 
> https://github.com/JuliaLang/julia/contributors
> 
> 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.

[`repl-readline.c`](https://github.com/JuliaLang/julia/blob/master/ui/repl-readline.c)
is licensed under the GNU General Public License Version 2:

> Copyright (c) 2009-2012: Jeff Bezanson, Stefan Karpinski, Viral B. Shah.
> 
> This program is free software; you can redistribute it and/or modify
> it under the terms of the GNU General Public License as published by
> the Free Software Foundation; either version 2 of the License, or
> (at your option) any later version.
> 
> This program 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 General Public License for more details.
> 
> You should have received a copy of the GNU General Public License along
> with this program; if not, write to the Free Software Foundation, Inc.,
> 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

External libraries, if used, include their own licenses:

- [AMOS](http://www.netlib.org/slatec/guide)
- [ARPACK](http://www.caam.rice.edu/software/ARPACK/RiceBSD.txt#LICENSE)
- [D3](https://github.com/mbostock/d3/raw/master/LICENSE)
- [DOUBLE-CONVERSION](https://code.google.com/p/double-conversion/)
- [DSFMT](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/LICENSE.txt)
- [OPENLIBM](https://github.com/JuliaLang/openlibm/blob/master/LICENSE.md)
- [FADDEEVA](http://ab-initio.mit.edu/Faddeeva)
- [FEMTOLISP](https://github.com/JeffBezanson/femtolisp)
- [FFTW](http://fftw.org/doc/License-and-Copyright.html)
- [GMP](http://gmplib.org/manual/Copying.html#Copying)
- [LAPACK](http://netlib.org/lapack/LICENSE.txt)
- [LIBUNWIND](http://git.savannah.gnu.org/gitweb/?p=libunwind.git;a=blob_plain;f=LICENSE;hb=master)
- [LLVM](http://llvm.org/releases/3.0/LICENSE.TXT)
- [OPENBLAS](https://raw.github.com/xianyi/OpenBLAS/master/LICENSE)
- [PCRE](http://www.pcre.org/licence.txt)
- [READLINE](http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html)
- [RMATH](http://www.r-project.org/Licenses/)
- [SUITESPARSE](http://www.cise.ufl.edu/research/sparse/SuiteSparse/current/SuiteSparse/)
- [ZLIB](http://zlib.net/zlib_license.html)