Yes, as long as there is no pressure placed on colleagues to make a purchase and it interferes with neither your working hours nor the work facilities made available by CERN.
The Staff Rules and Regulations (R I 13.04) require the prior written authorisation of the Director-General for members of personnel making any communication outside the Organisation in which they identify themselves as such or make references to CERN’s functioning or activities.
In addition, you should remember that the novel should be written outside your working hours and its content should be compatible with your obligations as a CERN contributor, in particular your obligations of reserve, tact, discretion and confidentiality. You should advise your Department Head who is best placed to assess this compatibility.
You should seek prior authorization from the Director-General before agreeing to give the lecture. Even if you receive authorization, you may not derive personal benefit from the activity because it is connected to your expertise at CERN. The Finance and Procurement Department should invoice the event organizer for the agreed remuneration plus any additional costs to CERN, such as travel or per diem expenses. Furthermore, you should inform your Departmental Planning Officer in order to make the relevant financial arrangements.
Employed members of personnel must obtain the prior authorization of the Director-General before accepting a teaching position.
Yes, provided that you participate without your connection with CERN being identifiable.
Discuss the situation with your hierarchy. You should not work on any task that could create a conflict of interest, or the appearance thereof, between CERN and your future employer.
Bear in mind that your obligation not to disclose any confidential information you have acquired in connection with your work at CERN continues to exist after you leave the Organization.