Brazil’s lottery used to run off proprietary software, costing them a lot of money each month in maintenance, but more importantly restricting their ability to create new games which meant restricting and delaying new revenue. Also important, of course, was the stability and dependability of the software. For this they chose Debian GNU/Linux.
The use of Free Software reduced their time to deployment of a new game from ten months to three weeks.
Thanks to Caixa Economica Federal and 4Linux