Scribus will download scribus_spell_dicts.xml to check for spell check dictionaries.
Scribus will download scribus_hyph_dicts.xml to check for hyphenation dictionaries.
Scribus will download scribus_fonts.xml to check for fonts.
Scribus will download scribus_help.xml to check for help files.
Scribus will download scribus_palettes.xml to check for help files.
Opening the above files in a text editor will tell you where the files are coming from. Typically, their home page.
Scribus will download scribusversions.xml
to check for upgrades if you tell it to from the Help menu.
This site serves only this purpose. Thanks!