Ecopath with Ecosim is developed with Microsoft Visual Studio, using the Visual Basic .NET programming language. As such, if you plan to work with the EwE source code, you will need to have a computer system that is able to run either Visual Studio 2010 (or newer), or Visual Basic Express 2010 (or newer). We recommend installing Visual Studio 2015 Community Edition (free)
September 2016 update: Up to versions EwE 6.5.X are compatible with Windows XP Service Pack 3 and .NET framework 4 Full (not Client!). EwE version 6.6 will only run on Windows Vista or newer.
EwE and Visual Studio/Visual Basic run on Macs using virtualization. Windows versions that can host the EwE development environment are Windows Vista or newer.
To run EwE you will need to have .NET Framework 6 installed. There is no nice way to validate the installation. However, the EwE setup program will make sure your system is up to date.