No, you do not need to send a message to the app.
If you scan with this setting the app will get this information via TW_IMAGEINFO structure which you need to update of course.
This depends on which sample code you refer. But basically if you respect the copyright of the working group members names in the file headers, it is no problem to use it for a printer driver.
Anyhow starting from a 1.x sample source it is not a low hanging fruit to come to a robust driver.
Best regards,
Kaij