They explicitly answer this question in the FAQ (sketchapp.com/support/faq): Is Sketch available for Windows or Linux? Due to the technologies and frameworks

They explicitly answer this question in the FAQ (sketchapp.com/support/faq): Is Sketch available for Windows or Linux? Due to the technologies and frameworks exclusive to OS X that Sketch has been built upon, regrettably we are not considering supporting Sketch on either of these platforms.