Opencola, who was sold to Open Text Corporation in 2003, was a company that started out creating a collaborative searching software which would be completely open-source. In 2001, the company decided to use its name to its advantage and create an open-source cola as a promotional tool to explain open-source software, which they also named OpenCola.
After 150,000 cans of the cola were sold, it was apparent that the cola was much more than just a promotional tool. Just like software, the cola went through multiple revisions before arriving at its current version of 1.1.3. When referring to software, open-source means that the source code—the lines of code that actually make up the software—are available for anyone to view and modify.
A good example is the open-source web browser Mozilla Firefox. For the cola, it means that the recipe is available for anyone to view or modify for their own use.
This is on the other end of the spectrum from Coke, whose recipe is kept a secret and currently held in a secure vault at The World of Coca-Cola exhibit in Atlanta.
The recipe for OpenCola is under the GNU General Public License (GNU GPL), which guarantees anyone the freedoms to use, share, copy or modify the software, or in this case, recipe. The only stipulation for OpenCola is that anyone who modifies the recipe must also license it under the GNU GPL.
In addition to the recipe itself, the company provides instructions for making home-made soda water from basic ingredients such as yeast and sugar. This is to avoid the need for anyone to have to purchase commercially produced versions or machines and effectively keep the entire process open source and doable for everyone.