Open Source vs Shared or Collaborative Source

With the OSI talking to Microsoft, there's been a lot of "shared source" in the news lately. The idea is pretty interesting: Paying customers (or, in some cases, significant contributors) are allowed access to the source code. Thus, the benefits of open source can be achieved without the "tragedy of the commons," where users can take from open source without ever giving back.

Is this a better model than open source? It depends:

• You are able to collect payments from your users, but then you're back to selling those users again. For an established vendor, that might not be a big deal. For a startup, this cost could be significant.
  
• If the users can make significant contributions in return, then enforcing payment to develop source code will just add the cost of "selling" to the overhead of creating software. Note that significant contributions could happen even if only a small percentage of users contributed, if there were enough users to start with.
  
• If you're competing against a true free open source alternative, a "shared source" model would be a pretty tough sell, unless you already have a lot of brand recognition or trust amongst users. Why would anyone pay to get the source code when they can get it free somewhere else?
• Even more dangerous is the possibility that after a while, the free alternative becomes so widespread that it becomes a standard. Your for-pay shared source cooperative does well for a while, then fades.

It seems to me that shared source is a step forward for established vendors in giving more participation to their users. It may also work in narrow niche markets where open source hasn't arrived...yet. For startups or broad market technologies, though, open source is probably still the better option, especially if they might end up competing against open source alternatives.

In other words, shared source probably works better for Microsoft than the rest of us.