Søren Go to settings and turn off linear interpolation in Spine. At runtime you will need to render with filtering set to nearest. Can't give you exact advice on that without knowing which runtime you use.
Søren If you use a framework or engine (like Unity or libGDX) you require a runtime to use the data unless you're just exporting PNG sequences or spritesheets. If you aren't doing anything like that, then you can ignore my comment about runtimes 🙂