In Tcl 8.6.16:
% package require ftpd
1.4.1

In Tcl 9.0.2:
% package require ftpd
can't read "tcl_platform(user)": no such variable
% namespace eval ::ftpd {variable contact;set contact hostname]"}
% package require ftpd
1.4.1

From help of global:
This command has no effect unless executed in the context of a proc body.

With the following modification the script completes successfully:

--- 2024-10-24 18:47:54.000000000 +0900
+++ ftpd.tcl    2025-07-23 02:19:48.243683100 +0900
@@ -20,8 +20,7 @@

     variable contact
     if {![info exists contact]} {
-        global tcl_platform
-       set contact hostname]"
+       set contact hostname]"
     }

     variable cwd