Solution : https://service.sap.com/sap/support/notes/1013977 (SAP Service marketplace login required)
Key words :
query string parameters, user master data, current logon language, logon language defined, portal logon language, logon language, language defined, portal user, broadcasting wizard, choose 'execute'
Related Notes :
| 1008713 | BI JAVA: Logon language of BEx Web Applications Java |