Every single piece of software used on the PEG Judge is licensed under a free software license, such as the GNU General Public License. Here are the major components of the Judge:
- Debian 7 (Wheezy)
- Apache 2
- PHP 5
- GNU C and C++ compilers (gcc/g++)
- Free Pascal (fpc)
- Glasgow Haskell Compiler (ghc)
- Netwide Assembler (nasm)
In addition, your connection to the Judge (if you use the secure site) is encrypted using OpenSSL. The Judge is administered through OpenSSH and FreeNX and versioned using git. Nice mathematical formulae on some problem descriptions and analysis pages would not be possible without LaTeX and ImageMagick. The Judge hosts its own DNS using BIND, as well as its own mail server using Postfix and Dovecot. The forum is powered by phpBB, and the wiki you are reading now is, of course, powered by MediaWiki.
In addition, all of these components are free in the sense of costing nothing.