This degree of customer control is unheard of in the traditional proprietary software model. Even customers with unusually powerful financial leverage risks disruptions due to a traditional software vendor's internal problems or acquisition by another company. Several studies have shown a dramatic advantage in reliability for open-source software compared to most comparable commercial products. More effective development models, massive independent peer review for both code and design, and greater pride of authorship all contribute to this phenomenon. Some companies even go so far as to offer rewards for finding bugs in their software.
Source code is crucial for debugging and understanding how a product works.
In large software companies, few employees have access to source code, and the employees who have access are rarely available directly to customers. Access to source code is also essential for finding and fixing security holes and other undesired behavior. Some open-source products, including several of those listed above, have been so successful that they have no viable commercial competitors. Open source gives customers a much greater ability to customize software to fit their business needs. Large organizations can reap substantial cost and labor savings from even minor customizations when deployed on a large scale.