They find exoplanets and brown dwarfs all the time. This one just happens to be near the mass which differentiates them from one another. Nothing really mysterious about it.
Exactly. And there wouldn't be anything particularly strange or unusual about it orbiting a star, as most stars are binary and orbit around another star, or, more precisely, both orbit a common center of mass. And surely it is the case that many of these systems involve a star and a brown dwarf, which, as you and the article states, is simply an object which didn't have quite enough mass to ignite and become a star itself. ie, a "failed star".
In any case, the article contains lots of good general info on the topic which serves to educate interested and curious folks who may not have known these things previously.
The fact that most of the exo-planets that have been discovered, via the far more common "star wobble" method, are these humongous giants several times the mass of our Jupiter, is not at all surprising either, since, being so massive they are the ones that would have the most noticeable gravitational effect on their host star and be detected (would tug on the host star more).
Same goes for the eclipsing binary method as well, where one large object, usually another star, moves in front of another causing that star to dim periodically. With either of these methods a planet anywhere near earth-sized would be very difficult if not impossible to detect, at least at this point with the current level of technology.