Ah - these are the details about which I'm not so very enthusiastic myself, so I seldom discuss the tools with Sami. So, at the moment I don't know exactly what setup he uses at the moment. The way I see it, when writing source code, it is the source code that matters =)

So, this is what little I know:

Yes, Sami uses Windows on a desktop PC. And I think on the side he has an old mac book for Mac-specific testing and debugging. UnReal World is written in a mixture of C and C++, using SDL2 library for sound and graphics. I'm not sure exactly which IDE Sami uses. My contributions to UrW coding always start as fully isolated "modules", so I'm not working directly with the entire UrW codebase. And depending on the size of the project, I've been working with Geany, or Code::Blocks - then, once I get the stuff working, I hand it over to Sami so he can integrate it to the rest of UrW, and that stage often involves a little modifications needed for my code.

For Ancient Savo development I wanted to experiment with something which would not be a ready-made engine, but would easily be cross-platform compatible also with mobile devices. So I chose libGDX as that looked promising, and since it is in Java, I needed to change language. For IDE I use IntellijIDEA, running on Debian MATE linux.

Both for UnReal World and Ancient Savo there are private version control systems, to sync and to back up the code.

From my point of view, the Ancient Savo project could also replace the old console-based approach of me developing and testing isolated modules of source code for UrW. But, to make that smoothly integrated, I either need to learn a way to include C++ code in a Java project, or pick up some semi-automated tool to convert between these two languages. Or, possibly just leave Java behind and work in C++. This is the future perspective in two to five years perspective, in case that Ancient Savo reception will be good enough to warrant starting to work on a sequel project, and then designing that sequel project so that it would be more handy to produce code to be adapted and integrated to UrW as well.

For Ancient Savo I just manually converted the weather simulation C++ source to Java code. The random map generator I just re-wrote in Java. And I see this mostly as a way to learn - in the coming years I need to learn more based on this experience.