Here is first screenshot of Sciter running on Mac.
I am using JUCE library created by Jules Storer as a backend here. JUCE also supports Linux, Android, iOS so I expect ports on these platforms to be available pretty soon too.
Here is the same document opened in S3 with native Windows backend. There are some differences in rendering details, working on them. Intention is to have rendering as close as possible but some differences will be there for sure, e.g. fonts are rendered differently and set of fonts is different on each platform.