Is it possible to put some classes into a DLL?
I have several custom classes in a project I am working on and would like to have them put in a DLL and then accessed
Use runtime packages for this purpose; it's exactly what they're designed for in the first place. They get loaded automatically (or can be loaded manually), and automatically set up the sharing of the same memory manager so you can freely use classes and types between them.
You're much better off using packages (which is exactly what the IDE does for much of its functionality for that very reason).