This paper presents a Dynamically Configurable Modular System (DCMS), which is a library for the development of applications with an open architecture. The DCMS is oriented to a wide set of applications, such as mathematical simulation, Web technologies, and so on. By now, the library has been used in the WinALT simulating system, and the knowledge base and the portal development. The substantiation and description of the DCMS architecture are given. A number of applications, based on the DCMS are discussed. Such features as simplicity of maintenance and usage, adaptability for the user’s requirements are gaining more importance in order that a complex software be successfully developed. The concept of open software architecture give rise to facilitating the development of software with these features.