pet stores like Petsmart and Petco don't sell the EBJD. But they do sell the regular Jack Dempsey usually. Which are more aggressive than the EBJD. They won't work with the Goldfish, they'll nip their fins. The betta fish can be put in a little fish bowl. If you get a small goldfish and a small EBJD they should be okay together....the EBJD grow pretty slow, so the goldfish will definitely grow faster than the EBJD. Make sure you are getting a 55 gallon soon, because the EBJD and goldfish won't be too happy stuck together in the 20 gallon. I only kept mine with goldfish cause I was waiting for my 110 gallon to be ready for my EBJD.
And I'm sure other people would recommend not even doing it.
Make sure the temperatures for the EBJD and goldfish are similar. The EBJD are pretty fragile, and they like their water warm. I keep mine at 80-82. So a heater is a must, even though the goldfish don't need one(but it's good to have one for them too).
If possible...you should wait on the EBJD till you have a tank set up for him. They need to be the "boss" of the tank, it keeps them happier and gives them a better chance at making it to adulthood.
-It also seems like the betta would probably be bullied or killed by the oranda...I think they're a little more aggressive? so you should keep the betta in a bow or vase if you can, just change the water out weekly.
ask the people at the pet store what they think about the oranda and betta together.