Sciter 3 is all about various ports on various platforms.
For example here it runs on Windows XP where it uses GDI+ graphics backend:
Sciter 3 is built on top of Sciter 2 codebase and is a drop-in replacement of Sciter 2 – you just need to replace sciter32/64.dll in your distributions. Sciter ABI stays the same.
I expect first public build of S3 to appear September 7th this year (2013).
Sciter for Mac OS X will appear later this year.
I am also planning to do Linux/Gnome port but I am not sure about its dates yet.