Just got my copy of Pro Drupal Development in the post. Very exciting. The first chapter has just been published as an article on Dr Dobbs. I hope nobody minds if I quote at length from the forward by Dries Buytaert, because I think it says everything:
"... on January 15, 2001, I made Drupal available as Free Software.
"Since then, everyone has been able to download Drupal free of charge. Anyone can run, copy, and modify Drupal and even redistribute modified versions of it—as long other people are given the exact same rights, as spelled out by the GNU General Public License.
"Making Drupal freely available was a great decision. The key benefit of using Drupal is not its ease of use or its functionality, though these are important. Drupal’s unique value lies in the facts that the project is open and accessible and that there are very few limitations on what you can do with Drupal. What sets Drupal apart from other systems is its thriving community, a direct product of the openness and transparency. The Drupal community is what makes Drupal tick, and the way we, as a community, develop Drupal is what makes it so successful.
"Think about this for a moment: what are your chances of becoming the world’s foremost expert on a proprietary content management system (CMS) or on proprietary software in general? Unless you’re working for the company owning the software and you get access to proprietary documents or high-level meetings within corporate walls, your chances are slim—you simply won’t get access to all the internal information.
"Contrast this scenario with Drupal development. As a developer, you have access to Drupal’s complete source code. You can read up on all the discussion that led to any design decisions, and you can tap right into the brains of the best Drupal developers in the world. In fact, there is nothing that stops you from becoming the best Drupal developer in the world. The only limitation is your willingness to learn."