Program D is the most widely used free ("open source") AIML bot platform in the world. It is the most feature-complete, best-tested implementation of the current AIML specification. It supports unlimited multiple bots in a single server instance, and has an open-ended architecture for interacting via any interface imaginable. The standard release provides a J2EE web application implementation that can be deployed as a .war file. Drop-in listeners are available for IRC, AIM, and Yahoo. It includes an automated testing framework for testing knowledge bases, and is packaged with an AIML Test Suite that verifies that the program itself complies to the AIML specification.

Program D is known to work with many different languages / character sets. Its component-oriented architecture allows it to be integrated into any application framework desirable. It is implemented in Java, and uses many features of the latest JDKs to provide optimum code reliability.

Although Program D sees only occasional bursts of development, it is in constant use for projects of varying size, in projects ranging from artistic work to academic research and commercial applications.