I'm curious how you are trying to accomplish the split-screen usage. Are you just grabbing the window frame and dragging it to the side of the window, taking advantage of Windows' feature where it will automatically size that window to fill half of the screen and then prompt you to select a second app to take the other half? Or are you using some other method?
Regardless of how you're doing it, your technique will probably only work with apps that run inside windows. iFly does not--it is exclusively a full-screen app.
You can, of course, use Alt-tab to swap between iFly and other apps on a Windows device. Depending on what you're trying to do, briefly overlaying a separate app window on top of iFly in the background may be an acceptable workaround.