From the AVsitter website

Experience Keys

Second Life has now enabled ‘experiences’ which will allow automatic attachments (without need for any permission request).

To get the benefit of automatic attachments with AVprop:

  1. Users will need to enable the experience ‘AVsitter’ (by Code Violet) on their land. An experience may be enabled at the estate level or the parcel level by adding it to the Allowed list for the estate or parcel. Experiences are enabled under ‘About Land’ in the SL viewer. For an excellent explanation, see this video by Froukje Hoorenbeek.

You can find out more about ‘experiences’ on the SL blog and in the SL scripting WIKI.

!! If users do not enable the ‘AVsitter’ by Code Violet experience then each prop will require permission to attach and the owner may receive the message “To enable auto-attachments, please enable the experience in About Land.” (discussion)