DigSim Development
Components
To create and integrate new components you have to implement a java interface. Here is the implementation of a simple logical not component: Inverter.jav
You should download the sources of the whole project to understand the logic behind it.

Application
If you want to change the editor itself, download the zipped sources: sources_v0.06.zip. Read the short description of the internal structure, before you start modifying the code.