SpineCreator is built using the Qt toolkit http://qt.io, a cross-platform library of C++ code for building desktop apps. This means that SpineCreator can be compiled on Windows just as well as on Mac or Linux. However, we only support Mac and Linux at present as “first class citizens”, due to a lack of developer resource.
SpineML_2_BRAHMS in particular would require some work to function on Windows, as it includes bash scripts. Microsoft have recently added bash for Windows 10 developers, so in the near future it may be easier to bring the SpineML toolchain to Windows.
For now, if you would like to use SpineCreator on Windows as an editor (without the use of the simulator back-end), then please go ahead and install Qt, graphviz and python, then compile SpineCreator in QtCreator.