Looking at an open source model in the same way:

• The project administrators are typically the engineers doing much of the development and design and also setting the project roadmap.
• The road map is owned by the project administrators. In this respect they are partially fulfilling the role of Product Managers. The project administrators do not perform the other, 'whole product' focused, roles of Product Managers.
• The community participates in many roles and tasks involved in designing, implementing, and testing the software.
• There is no 'Go To Market' process in this model. This is why the barriers to the adoption of open source listed above exist.
• There is no 'Whole Product' in this model. There is software, but not in an easily deployable or managable form. 
• There is no marketing in this model so open source projects gain mind-share through technical articles, blogs, and word-of-mouth.

A few people have a negative reaction to the open source concept because they think it is in some way socialist or communist. This is not the case: open source is effective because the motivations of all participants are naturally aligned (rather than artificially aligned with financial reward as a 'pseudo-motivation').

Next - The Professional Open Source Model