As of Q2 2015, Telerik Reporting uses the standard .NET licensing mechanism, which means that using Telerik Reporting items in design-time causes Visual Studio to add a license.licx to the solution. This file is used only in design-mode and is not needed for deployment explicitly. The .NET framework (lc.exe) will embed it in the assembly when your Application is built for deployment.
The license file is maintained by Visual Studio and contains information about all licensed components in the application (including non-Telerik products).
Having this license file is not expected to bring any performance/compilation issues and you can ignore it.
In case your project build fails with errors pointing to the license file, you can delete it and rebuild.
If you are working under source control, once the file is created, it will be detected as a change by your source control system. We would suggest that you check-in this file initially. Then, when it is checked-out again during your work, it is up to you to decide whether to check it in, or discard the changes.