The listing of available arguments for the fglcmd -cmd agent:activate does not have a timeout option but there is a nowait argument you might consider:
-nowait Do not wait for agents to finish processing this command
The cmd is issued and does not wait for the result.
ie ./fglcmd.sh -cmd agent:activate -name JavaIntegrator_on_malibu -nowait
You can use fglcmd argument angent:list to get agent status or use the Agent Status dashboard.