Since releasing information regarding our module and plugins API we’ve had several dozen inquiries from developers. Some have indicated specific ideas, others have more general interest. Lots of plugins have been written and released, and one module that I know of.
Our ExpressionEngine module and plugin license allow you to do what you want with them, including selling them.
Having said that, plugins, by their nature, are very small enhancements. Selling plulgins, while legal, violates the spirt of plugins as freely distributable enhancements. We don’t plan to ever sell plugins, and thus far, no third-party developer has either. We actually discourage the sale of plugins.
Modules, on the other hand, are larger, more involved enhancements. Often, modules include backend features, accessible through the control panel. Modules require more development effort than plugins, so depending on the scope of the module, it may be justifiable to sell it. It’s certainly legal.
On our modules page, we have indicated that we may even provide a venue in our store for developers to sell their modules if they meet the following criteria:
1. The code-based must meet our coding standards and be rock solid in terms of security.
2. The developer must be committed to providing responsive technical support and must represent our brand in the highest manner possible.
3. The development commitment (now and on an ongoing basis) must be great enough to warrant selling the module. We are not interested in selling small enhancement that don’t require much effort, only ones that provide significant new capability, or allow us to penetrate vertical or other new/niche markets.
Regarding pMachine (Free or Pro): This product is a different animal than EE. It doesn’t have a plugin/module architecture, so it’s going to be difficult to distribute an enhancement without distributing parts of the core system itself. Distributing the core isn’t allowed.
So in summary, EE is the better platform for plugins and modules than pMachine, and as long as you do not distribute our core system or components from it, you are free to do whatever you want with your enhancements.