VirtualBox and Mountain Lion (Mac OS X 10.8)

[Update:

VirtualBox 4.1.20 and later are now completely compatible with Mountain Lion and this jiggery-pokery is no longer needed

- FB]

Apple released Mountain Lion (Mac OS X 10.8) late last week and a few people are stumbling over installing VirtualBox on it, so here are a few tips:

At the time of writing, the current version of VirtualBox is 4.1.18. Strictly speaking, this is not commercially supported, but VirtualBox users tend to be an intrepid and gung-ho bunch, and will try to run it on Mountain Lion anyway. They'll download VirtualBox and run the installer by clicking on the VirtualBox.mpkg icon:

...and get a message like this:

This will happen if you are using the default Security settings of Mountain Lion for downloaded applications, which probably look like this:

To get VirtualBox installed you can either:

1. temporarily allow applications downloaded from Anywhere in the System Preferences box above, changing it back after installation; or
2. hold Control key down as you click the .mpkg and choose Open. Doing this, you'll get a subtlety different dialog like this:

-FB 

 P.S. You can expect to see a "Fully Supported" version in the not too distant future