If you grab the tar file at
http://www.arsdigita.com/free-tools/uptime.html, the only thing in
uptime/uptime/data-model.sql that needs to be changed is the definition for the
uptime_stale_p function. The rest of the data model (the tables, index, & sequence) work perfectly well in either Oracle or Postgres.
Seems odd that ArsDigita would cancel this service, which obviously does not require much bandwidth or effort to keep going. Maybe a little tweak at Philip on the first day of the trial?