Due to the high usage of this guide and the lack of comfort in Gist's commenting area, I decided to make a blog post out of this which you can find here:
http://blog.frd.mn/install-os-x-10-10-yosemite-in-virtualbox/
https://www.youtube.com/watch?v=tafqhSUfKnY points to: https://drive.google.com/folderview?id=0B9oZd81xqtTOckJOT25uTzVfT3c&usp=sharing The file Key.text made everything work for me under GNU/Linux+VBox 4.3.18!
VBoxManage.exe modifyvm "MacOS" --cpuidset 00000001 000306a9 04100800 7fbae3ff bfebfbff
VBoxManage setextradata "MacOS" "VBoxInternal/Devices/efi/0/Config/DmiSystemProduct" "MacBookPro11,3"
VBoxManage setextradata "MacOS" "VBoxInternal/Devices/efi/0/Config/DmiSystemVersion" "1.0"
VBoxManage setextradata "MacOS" "VBoxInternal/Devices/efi/0/Config/DmiBoardProduct" "Iloveapple"
VBoxManage setextradata "MacOS" "VBoxInternal/Devices/smc/0/Config/DeviceKey" "ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc"
VBoxManage setextradata "MacOS" "VBoxInternal/Devices/smc/0/Config/GetKeyFromRealSMC" 1
https://techsviewer.com/install-macos-sierra-virtualbox-windows/