The wonderful Les Barker reads his own poems from a book, or at least usually has it in front of him.

The objection to people reading, whether poems or songs, is that in most cases they do it because they haven't acquired performance skills, and while they continue to rely on this they won't gain these skills. With these people, reading detracts from the performance. There are those who can deliver an effective performance while reading, but they are very much in the minority.

The presumption, out of respect for the song and the audience, should be to learn it properly and perform from memory. If you can't do this, consider whether you are ready to perform it yet. If you have genuine problems with memory, then learn the skills to deliver the song effectively from a prompt.