Many network equipment vendors have different generations of devices still in operation in the field and their users are still happy with them because after years of use they still do the job. Sometimes though some upgrade is done to the network and new functionalities are required for the old devices in order to spare a huge investment to replace them completely with new generation devices.
The sources for the respective device version have been considered obsolete for quite some time now, they only exist on some backup server and they used to compile on one of the first Ubuntu versions. They no longer compile on any modern Linux distribution.
Over the years all the people who were familiar with that product either left the company or got assigned to new roles and new products bringing new revenue so nobody is available to take the task in time to...