Versions of Reporting Services
There are four versions of Reporting Services to choose from: the Standard Edition, the Enterprise Edition, the Developer Edition, and the Evaluation Edition. Except for the Standard Edition, all provide the same feature set and differ only in EULA  license terms and time-bomb duration before the code stops working:
The Evaluation Edition stops working after 120 days and is licensed only for evaluating the product.
The Developer Edition differs from the Enterprise Edition only in that it's licensed for development but not for production use.
The Standard Edition and the Enterprise Edition are the only editions licensed for production use and for using the features described in this chapter.
The Standard Edition is limited in that it does not support web farms, custom security extensions, report history, and data-driven subscriptions, and it's limited to not more than four processors and 2 GB of RAM.