Eplusplus is completely free for development. All you have to do is register as a developer and then you may download a copy of eplusplus to install in your development environment free of charge.
When you are ready to deploy your web application you must procure a deployment license. The license fee for a deployment license is $495 per server CPU. The deployement license covers ALL e++ applications that run on that server. The license includes the runtime language environment (which includes the interpreter) and the high-performance relational database.