I currently have 3 Blue Paradise Gourami; sharing the same tank with a Betta...
Neither have killed the other yet... the Betta ignores them, and they ignore the Betta... until its feeding time of course then the Betta will get picky and try to chase them away from the food it wants. Otherwise, they're all pretty docile.
Now; if I were to add in say, an Angel Fish... that then Betta will go nuts and peck the hell outa the Angel; I seen it happen and ended up with a dead $10 Angel as a result...
There is also a pair of Leporinus Fascitus in the tank with them; one of them a 4" and the other a 6" - 7" ... there is also a pair of Rope Fish; and a pair of 2" Pleco's.
The most aggression that I have seen; is from the larger Leporinus; whose a bit picky about "his territory" in a nice dark corner under some artificial wood.
So sure; if your tank is decorated well enough then you can keep a Paradise Gourami together with a Betta; cause they'll both have their own "safe place" if they feel they want to hide from each other... but in truth, I've watched mine actually hanging out in the same spot without problems; eventually one, or the other will just swim away and go somewhere else.
Wikipedia also states that Paradise Gourami can safely be kept with other similarly aggressiive fish, so long as there are others of their same breed to keep them company. so I have 3 of them... I have considered adding in a fouth but I suspect that anymore and my Betta might start to feel a bit more agitated and outnumbered... so for now I'm satisfied with the delicate balance I've created.