From OpenSCADAWiki
Modules of OpenSCADA are stored in the dynamic libraries. Each dynamic library can contain several modules of the various types. Filling of the dynamic libraries by the modules is defined by functional connectivity of the modules. Dynamic libraries suppose hot replacement, that allows you to make updating of the modules during work. The method of storage of the modules code in dynamic libraries is common one for OpenSCADA as it is supported practically by all modern OS. What does not exclude an opportunity of development of other storage modules code methods and most of the modules can be build in to the OpenSCADA core library excluding external files of the modules at all.