Its a cross!
Red Gubinge is a hybrid between Gubinge and Marul (Blackberry) and is not that common.
The fruit is much fuller and sweeter than Marul, however this is also dependent on seasonality of the fruiting period.
The fruits below were collected in Cygnet Bay with the Bardi Jawi Rangers as part of the restoration work being conducted in local vine thickets. This tree was targeted because of the sweet and favoured fruit. The seeds have been sown by SKIPA people at the Kimberley TAFE nursery and it will be interesting to see whether they germinate over this wet season.
The leaves of Red Gubinge are similar to Marul.
Society for Kimberley Indigenous Plants and Animals 
Whats the difference between the
Terminalia Petiolaris x Ferdinandiana (Red Gubinge)
and the
Terminalia Ferdinandiana – Gubinge – Billygoat Plum – Murunga – Kakadu Plum
The Red Gubinge is a cross between a Gubinge and a Marul tree. See here for more information: https://skipas.wordpress.com/native-plants/plant-families-a-e/combretaceae/terminalia-petiolaris-x-ferdinandiana-red-gubinge/
What about the properties … Does it have the same, like that of the KAKADU Plum ?