The most probable reason for not seeing the script initialization parameters is that the script code failed to compile. Do the following:
If you see error stating CozyRoc.SSISPlus library cannot be found, open Add Reference dialog (from script IDE menu: Project -> Add Reference ...). If the dialog displays libraries only from your ... Microsoft.NET\Framework ... folder, you most probably didn't install SQL 2005 SP2. SP2 includes support for libraries found in Microsoft SQL Server\90\SDK\Assemblies folder and SSIS+ library is deployed there by default. Manually copy CozyRoc.SSISPlus.dll to your Microsoft.NET\Framework folder and try again.