Solution : https://service.sap.com/sap/support/notes/1444941 (SAP Service marketplace login required)
Key words :
gmux library anymore, funtion modules ws_, function calls ws_download, symptom error, 20 sap gui, prerequisites, ws_execute, cl_gui_frontend_services
Related Notes :
| 1418688 | SAP GUI for Java 7.20: Graphics and GMUX functionality |