If the column comes from a script, the script could add a command that places the same data into the clipboard, and you could them put that command on the context menus for exe and dll files.
You can also use Tools > Print / Export Folder Listing to copy columns to the clipboard, but that will get you the whole folder's worth.
If the column is put into the file type's info tip, you can get at it by showing the info tip and then pushing ctrl+shift+c. (I just noticed this only works if you remove the ctrl+shift+c hotkey from the Edit > Copy Full Pathnames menu item. We've accidentally given both things the same hotkey.)
I wouldn't expect selItem.ShellProp("scp:TextVersion/Version") to return anything because "scp:TextVersion/Version" is a script column, not a shell property.
Does the script column do something different to the built-in Programs > Product Version and Module Version columns?
Yeah, we have text files (SQL scripts, config files, that kind of thing) where we have a version number in the text. This column shows a normal EXE/DLL version if present but also the 'text' version for those files.