To install it follow these steps:

1. Download JDK 7
2. Open the DMG
3. Run pkgutil --expand "/Volumes/JDK 7 Update 60/JDK 7 Update 60.pkg" "/tmp/JDK 7 Update 60.unpkg"
4. Go to /tmp/JDK 7 Update 60.unpkg
5. Open the Distribution file in your favorite editor (I recommend (Sublime Text)[http://www.sublimetext.com])
6. Change the function pm_install_check() to always return true
7. Run pkgutil --flatten "/tmp/JDK 7 Update 60.unpkg" "/tmp/JDK 7 Update 60.pkg"
8. Run open "/tmp/JDK 7 Update 60.pkg"

The installer should skip the OS version check and you should be able to install without any problems.