I agree with you. I started checking every source file, and I found a lot of headers like this.
# <language> translation for <program>
# Copyright (C) <year>
# <copyright holder> <email>
It doesn't say anything about copyleft, or gpl license, but the /debian/copyright file says the package is GPLed.
For example, on
xsane.po for Chinese:
# chines translation for xsane
# Copyright (C) 2004
# leolarrel <address@hidden
So I wrote to leolarrel asking about this file, and he said:
"this translation po file for xsane is GPL . I just copy main po file and apply
chinese translation . so I forget to check this line "# Copyright (C) 2004" "
Now, shall we assume that all the files with that kind of header are licensed under GPL, as the file in the debian folder says?, or do we have to send an email to the copyright holders in all cases?