   Questions on Porting and Integrating Open Source projects
  Im in the planning phase of developing an engine with a particular game in mind, however I have some questions (bear with me they may be stupid).Ive been an open source dev for over a decade and have finally gotten a good grip on C++. With this in mind Im developing an engine OpenPraxis (http://www.radicalpraxis.com/openpraxis/) with the idea of porting proven technologies into one modular system.I plan on taking an open source "Game Engine" (Renderer, Scene Graph, Script engine) and using it a base for porting the codebases of other open source projects as modules. These modules would be things like GIS, Vehicle Dynamics, AI, RPG functionality (stats, factions, inventory).So my question is what are the general practices involved in taking an open source project and "modularizing" it to work within another project. Would I develop an API, Hooks or what? I imagine there can be problems with library dependencies etc. Also are there any ethical problems here, assuming license agreements are upheld?Could anyone provide examples of this concept in practice?   