Is TWAIN compatible with application built using Ruby on Rails.
define ‘compatible’.
if you can do any of theses (from RoR):
access a COM object
call loadlibrary
receive and send(or post) windows messages
access a native dll
access a .net dll
then you have a shot at. I think a pure RoR twain solution is unlikely but if you can do any of the above you can probably access twain.