The OpenAccess core assembly and runtime assemblies are build against .NET 2.0 so that they can be used in all framework version above (and including) .NET 2.0. This shouldn't pose as a problem to your 4.0 application and will not cause any problems or performance hits to your application.
Please do not hesitate to let us know if you need further information.
All the best,
the Telerik team
Want to use Telerik OpenAccess with SQL Azure? Download
the trial version today.