Updated Ranking

Engine Code Viability Conceptual Fit What to Steal
Wargame Engine Alive (2024) Node-tree matches graph Rendering code, GUI, scene system
Fabula Dead (2012) Client-server matches exactly Architecture pattern, event protocol design
Sequtus Dead (2012) Low RTS patterns (selection, orders)
OpenRTS Dead (2006) Low Isometric tile concepts
Godot Alive Wrong runtime (GDScript, not Python) —
Panda3D Alive Wrong domain (3D) —
OpenRA Alive (C#) Wrong runtime, design patterns borrowable Trait system mental model, map format concepts