...oops. The problem's caused by my misunderstanding of WeiDU's language handling. I'll upload a new version soon, but for now, you can open up setup-d0tweak.tp2 in a text editor, search for "LANGUAGE", and replace that section with:
LANGUAGE ~English~
~english~
// ~d0tweak/english~
~d0tweak/english/d0tweak.tra~
LANGUAGE ~French (by Raphaël Mizrahi)~
~french~
// ~d0tweak/french~
~d0tweak/english/d0tweak.tra~
~d0tweak/french/d0tweak.tra~
LANGUAGE ~Spanish (by Bhasbuto/Clan DLAN)~
~spanish~
// ~d0tweak/spanish~
~d0tweak/english/d0tweak.tra~
~d0tweak/spanish/d0tweak.tra~
LANGUAGE ~Polish (by Damian Staniszewski)~
~polish~
// ~d0tweak/polish~
~d0tweak/english/d0tweak.tra~
~d0tweak/polish/d0tweak.tra~
LANGUAGE ~German (by Tanis Eichenblatt)~
~german~
// ~d0tweak/german~
~d0tweak/english/d0tweak.tra~
~d0tweak/german/d0tweak.tra~
It should then install successfully. Sorry for the inconvenience.