Is it proper etiquette to keep religious content on official course page?
In general, probably not, but there are cases where it might be reasonable. Religion is an immensely powerful force in human society, so inevitably it will impinge on science and sometimes it's appropriate to talk about that.

For example, the science of evolution has been under attack since its inception by those who believe in a literal reading of the Old Testament and other such texts. In a course on evolution it might be quite appropriate to present a quote from the Book of Genesis in order to discuss that opposition to evolution. What would not be appropriate there is to present it uncritically, casting young-earth creationism as some sort of equally-valid alternative to evolution.

Robert Oppenheimer apparently named the Trinity nuclear test after a religious poem by John Donne, and he famously quoted two passages from the Bhagavad Gita to express his reaction to the first nuclear explosion:


  If the radiance of a thousand suns were to burst at once into the sky,
  that would be like the splendor of the mighty one.
  
  Now I am become Death, the destroyer of worlds.


Those passages are tremendously evocative and have been re-quoted many times. There's even a Linkin Park album named for the "thousand suns" line. I wouldn't consider it improper for a text on nuclear physics to include those quotes.