Its functionality has been superceded by two packages (which are being maintained at CMU):

1. IPC (Inter-Process Communication) provides flexible, efficient message passing between processes. It can transparently send and receive complex data structures, including lists and variable length arrays. A wide variety of languages and operating systems are supported.
2. TDL (Task Description Language) is a superset of C++ that provides syntactic support for task-level control constructs, including task decomposition, task synchronization, execution monitoring, and exception handling. TDL facilitates building concurrent, autonomous systems.

While IPC and TDL are separate packages, they can be easily combined to achieve the same functionality (communication and task-level control) as provided by the Task Control Architecture.

If you really want to continue using TCA, click here for the original TCA web page.