Win8 boot loader will boot Win8 only unless you add a second OS to the BCD.
Grub can be used to boot both Linux and Win8 by chaining the Win8 BCD. Grub can also be used to chain OS X Chameleon or Chimera.
Chimera/Chameleon can be used to boot all OSs - OS X, Win8/8.1 and Linux distributions. It is, therefore, the easiest to use.