The site is owned and operated by Google and is named after its creator, Google employee Orkut Büyükkökten.
For OpenSocial development, Orkut is an attractive platform, despite its niche demographic (mainly Brazilians under 30) - because it is very easy to set up a developer "sandbox" account that can be used to explore deployment of OpenSocial applications that integrate with data from the Icodeon Common Cartridge Platform.
Once the an application has been developed in the Orkut "sandbox", the same application can be deployed to other platforms- such as MySpace - where perhaps the development environment is less comfortable to use or harder to set up.
You first need to sign up for a standard Orkut account and then for a "sandbox" at the following location: http://sandbox.orkut.com/SandboxSignup.aspx.
All that is required is name, company name and email - and you are ready to start deploying OpenSocial apps to "sandbox" - see screen shot above right and click for full size image.
Click for full size image.