I stumbled upon the SPACES Model for Defining Community’s Business Value blog post. The SPACES model looks like this:

1. Support – scale support and reduce costs
2. Product – get feedback to improve your product
3. Acquisition – get new customers  
4. Contribution – community contributes content
5. Engagement – increase customer retention
6. Success – help customers be successful using your product

The blog post talks about using the SPACES model to measure community’s value. I like this model. It shows the value the community can bring to other departments within the company. I believe this model with perhaps some modifications can measure developer relations program’s value and success too.