As mentioned above, you have to run an "upgrade from the local file system" to process the changes in the .info file. just restarting the server after updating the info file is not enough.
In order to access the global parameter, one has to use parameter::get_global_value [1] instead of parameter::get. it might be an option to work towards unifying these calls, there is an agenda-point for parameters in the the 5.10.0 agenda.
-gn
[1] https://openacs.org/api-doc/proc-view?proc=parameter%3A%3Aget_global_value