Upgrade has just published its monograph about Free Software. UPGRADE is the European Journal for the Informatics Professional, published bimonthly electronically. We have written a paper published on that magazine, and it is available here. The paper covers our study on the source code of the Debian 3.1 GNU/Linux system, one of the most popular and biggest Linux distributions in existence. In some weeks a spanish printed version will be available to ATI members. In the meanwhile, you can download here a spanish draft.