Sounds like artilery to me. It may not have really large shells but, I wouldn't want to be in that 50-meter wide, two mile long corridor when they arrived. Sounds like a new way of delivering cluster munitions. Could be very effective.
Also, the website compares the operation of Metal Storm to an inkjet printer head. An inkjet printer head heats up small droplets of ink and fires them onto the page. When you run out of ink, you replace the cartridge. Similar concept with Metal Storm. You load it with cartridges of barrels that are preloaded with ammunition and charges. Multiple cartridges with different types of munitions can be loaded all at the same time. When you run out, you replace the cartridges with new ones. Add to that computer controlled electronic fire control, and you have a weapon that can literally "print" an area with multiple types of munitions in whatever pattern is needed.
One of the videos shows a couple of Apache helicopters calling in a couple of UCAVs equipped with this system. The UCAVs, programmed with information gathered by the Apaches, pass over the target areas and, like a printer head, drop bombs in a predetermined pattern. They could actually bomb an area and leave a smoking smiley face on the ground. Heck, instead of scrawling messages on bombs as has been done in previous wars, we could literally scrawl messages with bombs. If it works as advertised, such fire control with such massive amounts of ordinance would in fact be revolutionary.