LiveCode Platform - It is Both Under the GPL and it is also Proprietary if using the GPL version the software you make...
AmpShell - AmpShell is a DOSBox front-end for Windows.
Microsoft Office Access - Access is now much more than a way to create desktop databases. It’s an easy-to-use tool for quickly creating browser-based database applications.
DBGL - DBGL is a free, open source, multiple frontends for DOSBox.
ESM Tools - ESM Tools is a powerful and widely known software development platform that comes with a centralized model infrastructure, providing the common frame for compiling, running, downloading, and organizing models (ones or multiple).
Terminal Launch V - For those that want a clean, simple fast emu frontend.