Thank you for contacting us.
As the message in your screenshot states, the current OpenAccess SDK version requires Visual Studio 2008 SP 1 or Visual Studio 2010. As Ivailo previously stated, Visual Studio 2012 support will be added in one of our upcoming releases.
You should be able to avoid the issue by just downloading the OpenAccess main installation package and leaving out the SDK for the moment. You can to access the installation package through the "Your Account" page on our website. Here's a direct link:
Download Telerik OpenAccess ORM Version: 2012.2 628 (Jun 29, 2012)
Let me know if that helps.
the Telerik team