You most certainly do not have to install the Telerik.OpenAccess.Adonet2.dll assembly into the GAC. When a project that uses OpenAccess is ran it is enough that in the output directory of the project, the executing directory contains the needed assemblies. As you know the .NET will first try and load the assembly from the GAC and if not there will try and look for it the executing dir, so having the assembly there will give you the expected result.
The assemblies you most probably need are Telerik.OpenAcces.dll, Telerik.OpenAccess.Config.dll, Telerik.OpenAccess.Runtime.dll and Telerik.OpenAccess.Adonet2.dll. Please have a look at this help topic explaining the problem.
However, if this is not the case please be sure to contact us back so that we can further investigate this issue.
the Telerik team