In TIBCO JasperReports® Server v6.0, the URL parameter &viewAsDashboardFrame=true does not work for embedding dashboards via the HTTP API. The parameter is fine in v6.1.0 however. In v6.0, instead the decorate=no parameter can be used for the new Dashboards. To repeat, this hindrance only exists in v6.0. Versions >= 6.0 can also embed dashboards using visualize.js, if an iframe is not desired.
The example URL below shows a sample of the URL string (in this sample is used Supermart Dashboard that is supplied with the software) that should be used to configure this feature:
Furthermore, if authentication is needed via URL (non secure method) then the j_username & j_password parameters can be used: