1. No, it's free.
2. It's a mostly text-based game, except for your map in the upper left hand corner. What you do is create a character, either a human or zombie. Then you are put somewhere in the city of Malton. Malton itself is comprised of many suburbs, each one a ten by ten square of buildings and streets. Each building, street, monument, etc. is a block, and you must move to blocks adjacent to your position to move across the suburbs. Now, the goal of the game as a human is to survive and hunt zombies. You can use weapons and items that you find in buildings, and gain more skills by levelling up. The goal of the game as a zombie is to kill humans and add them to the ranks of the undead. As a zombie, you'll also have the chance to destroy barricades and generally cause trouble for the humans. You will gain more skills as you level up as a zombie also.
The thing is, you only have a set number of Action Points to use. AP are used up when you perform certain actions, such as attacking something, talking or groaning, moving to a different block, etc. You regain AP at a rate of one per half hour. You have to use AP wisely, and judge your actions. For example, if you're a human, and you see a zombie two blocks away, but you only have 17 AP, what would you do? Well, you could either risk going to the zombie and trying to kill it, or you could try and get to a safe building. It's these decisions that make the game pretty challenging. In addition to AP, your IP address can only access a playing screen 160 times a day. It's set this way so that people who make multiple characters (Which you can do openly) can't just keep making characters to continue to play forever.
Now, a few other things. There are groups in UD much like the alliances of CN. They can be either groups of human zombie killers, or roaming hordes of the living dead. Some human groups choose to defend a specific suburb, usually the one in which that group was formed. Some zombie hordes choose to direct their assault to a specific suburb or building to cripple the human forces in that area.
Buildings can be barricaded by humans to keep the zombies out. There are different levels of barricading, according to how much AP the person constructing it uses to make it. At a certain point, the barricades become so strong that humans cannot enter or leave the building without the Free Running skill (Which lets you enter a building from an adjacent building). So you have to be careful as a survivor, because when you're low on AP and you decide to go to the nearest hospital, but you find it too heavily barricaded, you're as good as dead.
But one of the more interesting aspects of the game is that zombies can be revived. Using a special Necrotech (Sort of like the Ubrella Corporation of UD) syringes, you can actually bring the undead back to full life. There are blocks called revive points, where a group patrolling that suburb heals any zombies standing there. Cemeteries are always revive points, and it is against UD policy to attack any zombies standing in cemeteries (Unless they have Brain Rot, but you'll find out about those things later).
By the way, I didn't type all this out just for King, this is for anyone interested in Urban Dead.
Search "Urban Dead Wiki" if you wish to know all about the game.
The site is simply
www.urbandead.com