The error message: 
  invalid command name "-classonly::use"

The NoteBook widget uses (eventually) DynamicHelp.
DynamicHelp uses "-classonly", as defined in
$BWidget::use(DynamicHelp)

The proc BWidget::classes (utils.tcl, line 563) will
invoke "-classonly::use" for DynamicHelp.

The following context diff will fix it:

$ diff -c utils.tcl.orig utils.tcl
*** utils.tcl.orig      Mon Apr 17 12:19:03 2006
--- utils.tcl   Fri Jul  7 10:55:27 2006
***************
*** 567,573 ****
      set classes [list $class]
      if {![info exists use($class)]} { return }
      foreach class $use($class) {
!       eval lappend classes [classes $class]
      }
      return [lsort -unique $classes]
  }
--- 567,575 ----
      set classes [list $class]
      if {![info exists use($class)]} { return }
      foreach class $use($class) {
!         if {![string equal $class "-classonly"]} {
!             eval lappend classes [classes $class]
!         }
      }
      return [lsort -unique $classes]
  }

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Patch applied.  Thanks.

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Originator: YES

Here you go:

package require Tk
package require BWidget

proc do_write {} { BWidget::write [file join $::env(HOME) bwidget.out] }

Button .b1 -text "launch BWidget::write" -command do_write
Button .b2 -text Exit -command exit
pack .b1 .b2 -side top

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Do you have a sample script that illustrates this error?

File Added - 184182: bwidget.diff.txt

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that diff has lost its indent.  Let me attach a file...