According to publishers Droemer Knaur, based in Munich, the threats came from Islamist websites:
“He takes these calls seriously,” Knaur said in a statement on Tuesday.
Knaur said Salafi and Muslim Brotherhood sites had earlier posted a picture of the author with a caption reading “Wanted Dead.”
Leading Jama’a al-Islamiya member Assem Abdel Maged and Salafi preacher Mahmoud Shaaban had called Abdel-Samad an “infidel” during an Al-Hafez programme, after the writer delivered a lecture in Cairo last week criticizing radical Islamism in Egypt.
Here's an interesting video interview where he discusses his notions about Islam.
Apparently Abdel-Samad moved to Germany in the 1990s, and his dad was an Imam.