If you want your users to be able to retrieve the remaining files from Cryptshare 2 but to upload new files with Cryptshare 3.
If this option is active Cryptshare 3 will start up with an additional
reverse proxy configuration and forward Cryptshare 2 download requests to
the running Cryptshare 2 backend.
Additional requests made in this backend, such as clicking the 'about'
link will be intercepted and handled by Cryptshare 3. This way users will
only be able to visit the Cryptshare 2 download section if they still have
a valid download url.
Besides from turning off the Cryptshare 2 backend, you will not be
required to disable this mode manually within Cryptshare 3.
By the time all Cryptshare 2 downloads have been removed from the system
and the Cryptshare 2 upload directory is therefore empty, Cryptshare 3
will recognize this and disable this mode.