It would be legal. However, Quest currently relies on Windows Presentation Foundation; one of the few Windows libraries not to have a compatibility layer on other platforms. As it stands, there is no way to run Quest on a non-Windows device.
You can play games on mobile devices using the web version of the player; it's only the server that needs Windows in that case. So that would mean making an app which just launches an embedded web browser pointed at the web player for your game. This should work fine; but the game would require an Internet connection to work, and could suffer downtime when the server is overloaded.