Ok. That's it.
It would seem that LOGINserver has the same ability to re-add itself to the auto-launch list as does LoginItem. Because it was in two locations (loginwindow.plist and com.apple.loginitems.plist), getting rid of one wasn't enough: when loginwindow started up LOGINserver, LOGINserver re-added itself to com.apple.loginitems.plist.
However, just out of curiosity, I re-added those files to /Library/Preferences/ and rebooted. As expected, all the unwanted processes ran automatically. I then executed "./Library/Receipts/BrotherTWAIN.pkg/Contents/Resources/LoginItem global print", which showed this:
Index: 0
Full path to App: /Library/Printers/Brother/Utilities/Server/LOGINserver.app
Hide on launch: No
Executable Name: LOGINserver.app
So I executed "./Library/Receipts/BrotherTWAIN.pkg/Contents/Resources/LoginItem global remove-by-index 0"
I then re-executed "./Library/Receipts/BrotherTWAIN.pkg/Contents/Resources/LoginItem global print", which gave me:
There are no login items.
However: going to /Library/Preferences/ and double-clicking both loginwindow.plist and com.apple.loginitems.plist showed that LOGINserver had been removed from loginwindow.plist:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "
http://www.apple.com/DTDs/PropertyList-1.0.dtd
">
<plist version="1.0">
<dict>
<key>AutoLaunchedApplicationDictionary</key>
<array/>
</dict>
</plist>
but
NOT from com.apple.loginitems.plist:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "
http://www.apple.com/DTDs/PropertyList-1.0.dtd
">
<plist version="1.0">
<dict>
<key>privilegedlist</key>
<dict>
<key>Controller</key>
<string>CustomListItems</string>
<key>CustomListItems</key>
<array>
<dict>
<key>Alias</key>
<data>
AAAAAADaAAMAAQAAw2T2IQAASCsAAAAAACXlsQAl5bIA
AMKJeHIAAAAACSD//gAAAAAAAAAA/////wABABQAJeWx
AAKrAwACpusAAGHfAAAAHAAOACAADwBMAE8ARwBJAE4A
cwBlAHIAdgBlAHIALgBhAHAAcAAPABgACwBNAGEAYwAg
AG0AaQBuAGkAIABIAEQAEgA5TGlicmFyeS9QcmludGVy
cy9Ccm90aGVyL1V0aWxpdGllcy9TZXJ2ZXIvTE9HSU5z
ZXJ2ZXIuYXBwAAATAAEvAP//AAA=
</data>
<key>CustomItemProperties</key>
<dict>
<key>com.apple.loginitem.legacyprefs</key>
<dict>
<key>Hide</key>
<false/>
<key>Path</key>
<string>/Library/Printers/Brother/Utilities/Server/LOGINserver.app</string>
</dict>
</dict>
<key>Icon</key>
<data>
SW1nUgAAABwAAAAAU1lTTAAAABAAAAAAQVBQTA==
</data>
<key>Name</key>
<string>LOGINserver</string>
</dict>
</array>
</dict>
</dict>
</plist>
Seemingly, using Brother's own utility to remove what they added does not do the trick (which, given how Brother implemented this, and how ridiculously difficult this has been to diagnose, I'm not terribly surprised).
*_So, for those who just want the bottom line, here it is_*: to stop Brother's LOGINserver, USBserver, and NETserver from starting up automatically, delete the following files:
/Library/Preferences/loginwindow.plist
/Library/Preferences/com.apple.loginitems.plist
That's it.
If you want to get fancy, you can use Property List Editor to delete those specific dictionaries from the plist file, but just deleting those files should do the trick.
Thank you, orangekay, for all your help. This has been driving me nuts. Like a bad puzzle or something.
Yay!