Windows 10[]
Memrise is considering a Windows 10 universal app that will run on all your Windows devices from your desktop PC, phone, tablet, Xbox, Surface Hub, Hololens, etc. Vote for it here:
OS X[]
From the developer's page:
"Fluid lets you create a Real Mac App (or "Fluid App") out of any website or web application, effectively turning your favorite web apps into OS X desktop apps."