Based on what Column - Custom Text and Regexp does:
function OnInit(initData)
{
// DON'T add columns here.
}
function OnAddColumns(addColData)
{
// Add columns here.
}
function OnScriptConfigChange(configChangeData)
{
Script.InitColumns;
}
I'd expect the call to be Script.InitColumns();
with the brackets, but it probably works whether or not they are used, due to a quirk of how ActiveScripting methods/properties are implemented. The example script I linked didn't use them, so I left it that way, but I'd add them in unless it causes problems.