Bold Report Viewer can load reports from SSRS, but it does not use SSRS report processing for rendering of reports. The Bold Report Viewer will get only the definitions from SSRS such as reports, data sources and datasets. The data processing will happen in the application server that serves as the backend for the Bold Report Viewer. A connection is made to the data source using resource details retrieved from the SSRS Report Server and the connection string, query details used in the report. You can see the processing flow of a report loading in Bold Report Viewer from SSRS in the following image.
How to provide the permission for user to access the SSRS Report Server reports?