Both players had been linked with a move back to Glasgow from their present club Bordeaux-Bègles, but cutbacks meant that the Warriors could not afford them.
Both Bordeaux-Bègles and Bourgoin have been relegated despite not finishing the season in the demotion spots, with off-field problems with their finances being the reason.
Bordeaux-Bègles have failed to pay their players regularly during the season, having had problems with their shirt sponsors, who themselves are experiencing financial strife.