The pictures have a description indicating that it uses an unun at the feed point. It doesn't say what the turns ratio on the unun is, but that is how they are getting it to be multi/broad-banded. And they're using a bunch of short radials in an attempt to make up for the lack of the proper length radials.
The antenna will definitely work and you can have a lot of fun with it. Lots of people make/buy wire antennas with 9:1 ununs for portable use with much success. But there can be considerable loss in that unun, which you need to be aware of. The coax length recommendation tells us that they using that both to assist with impedance matching, as well as counterpoise (the coax shield).
it's a lot of $$ for an antenna like this, but you're paying for the price of labor to construct.
For your requirements, you might take a look at the Gap Titan.
