A bit of a misunderstanding. You should read some of Bryan Grieg Fry's work on this. He's classified most Colubrids as venomous despite not being dangerous to humans and not having a system for injecting their venom. Gonyosoma included.
So they're a bit like Garter Snakes which are also technically venomous. Their saliva can cause a bit of itching but is not anything to worry about.
I have 13 Gonyosoma and have kept several more. Their bites cause slight itching but I don't worry about it. Actually native Garter and Water Snakes cause more significant itching a redness for me.
Again, please track down some of BGF's work. He's made it very accessible to the hobbyist.
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Currently keeping:
3.5.5 Gonyosoma oxycephalum (Javan, mixed colors)
0.0.3 Rhynchophis boulengeri
0.4 Lampropeltis triangulum multistriata
0.0.3 Rhamphiophis rubropunctatus
2.1.2 Morelia viridis
1.0 Morelia clastolepis
1.1 Coelognathus flavolineatus
1.1 Pituophis catenifer pumilus
1.2 Charina bottae
1.1 Lichanura trivirgata