I have a notebook running OSX 10.8.2 and another notebook running Windows 8. Both of them are in the same network. Is there a software that, installed on both machines, allows the Mac notebook to use the Windows notebook as a second screen? (using network connection, no cables).
There is an almost identical question on the mac forums here https://discussions.apple.com/thread/2170310?threadID=2170310
You can use VNC Server on your windows computer, and any VNC screen-extending program to extend the screen.
Screen recycler is paid-for software that does exactly what you are looking for but there are other free solutions out there using VNC http://www.screenrecycler.com/ScreenRecycler.html
Synergy might be what you're looking for. It allows you to share keyboard and mouse between computers (and platforms - i.e. Windows, OSX, Linux) over a network connection, but have separate monitors. It is free, Open Source, & cross-platform software.
So, while you can't actually run OSX apps on your Windows monitor (or vice-versa), you can simply move your mouse pointer over to that screen and have instant access to Window. No need to move hands to a different keyboard or mouse.
Hope that helps!