Walter Briscoe wrote:

e) "Add a monthly season ticket to your Oyster card and you don’t
need to register it" I assume such tickets will be transferrable.
I can't find relevant part of Conditions of Carriage.
MOS at Oyster said only PAYG is transferable, But could not document
restriction. I raised a Service Ticket to get a formal answer.

Section 6.1.3
If you have a season ticket on your Oyster card or smartcard, you
cannot lend or transfer it to anyone else.

The chances of anyone catching you sharing a season ticket on an
unregistered Oyster card must be virtually zero, but it seems clear it
is not officially allowed.

Peter Smyth