muhammed and his followers stole materials from the Bible, Talmud, Pre-Arabian past and even from the Zorastran religion.
Why their hands were not cut off? As is too late the users of the stolen materials should be punished.
For unbelievers too koran recommends the same treatement:
إِنَّمَا جَزَاء الَّذِينَ يُحَارِبُونَ اللّهَ وَرَسُولَهُ وَيَسْعَوْنَ فِي الأَرْضِ فَسَادًا أَن يُقَتَّلُواْ أَوْ يُصَلَّبُواْ أَوْ تُقَطَّعَ أَيْدِيهِمْ
5:33, The punishment of those who wage war against Allah and His Messenger, and strive with might and main for mischief through the land is: execution, or crucifixion, or the cutting off of hands and feet from opposite sides, or exile from the land: that is their disgrace in this world, and a heavy punishment is theirs in the Hereafter; [Anyone who disbeliefs in Islam and speaks against it is considered to be waging war against Allah and his messenger]
http://cwis.usc.edu/dept/MSA/quran/005.qmt.html#005.033