Apart from actually being free to download, there's a lot more that's "free" about the Four Colour System. You are welcome to repurpose it for other than superhero role-playing, by removing superpowers and replacing them with skills or specialisms appropriate to the genre and setting in which you'd like to play. You can use it to aid in writing or converting adventures from one system to another... or just create and publish your own adventures for it.
So, what is it anyway? It's a basic toolkit for superhero gaming. The system it proposes is a simple one, using a percentage roll for task resolution, but it contains optional 'advanced' material... and of course you are encouraged to add on anything else you want. It is, however, suggested that publishers decide whether they want to use the Basic or the Advanced ruleset as a whole (unless they are going to write a complete corebook of their own using this as a basis).
After an introduction that explains all this, we get on to Characters, beginning with the determination of origin... or at least, the source of whatever superpowers they have. There's a table that you can roll on, or you may have a concept and prefer to select the most appropriate origin (the text assumes you roll, but...). Next the character gets Attributes - starting with seven Primary Traits: Melee, Coordination, Brawn, Fortitude, Intellect, Awareness and Willpower. Each of these is assigned a Rank, and they're used to derive Secondary Traits, which may be ranked or given a numerical value (each one differs). The Primary Trait Ranks are determined by a percentage die roll. If you have an idea in mind, you may wish to roll seven percentages then assign them appropriately, otherwise it is probably best to roll the Traits in order. Then you can pick mundane Skills as well as Powers, for both you roll a percentage to see how many you get. Then for Powers, you roll two more percentages, one to determine which one(s) and a second to give each a Rank. Again, the whole system is built about randomisation, but it should not be too difficult to deduce a mechanism for choosing Powers if preferred.
Next comes an exhaustive list of Powers and what they enable the character to do. Just about anything you have seen in a comic book or can dream up is possible if you consider these carefully.
Then, the next section is titled Playing the Game. The core of this is the Master Table, a multi-coloured matrix against which you roll a percentage every time you attempt to do something. If you remember the 1984 TSR Marvel Superheroes game, this looks very familiar! There are detailed explanations of how to use the Master Table to effect based on what you are doing, and what opposition you face, with particular reference to its use in combat. It is a lot easier than it sounds, and as you get familiar with it things begin to flow.
The final section is Gamemastering, and begins with the warning that this is more of a 'toolkit' than a full game. It goes on to look at various areas such as character health, ways of measuring luck or reputation, wealth and so on; before looking at how to incorporate vehicles into your game. It ends with a note on character advancement.
That's it. Naturally, you will have quite a bit to do in determining setting and creating adventures, but the bare bones, the framework is provided. Unlike the old Marvel Superheroes game, this system is well suited to devising your own superheroes (and villains, of course); although it ought not to be too difficult to codify your favourite heroes from comic book or screen if that's what you want to do. It's a neat package, poised to set you going saving the world with minimal fuss.
[4 of 5 Stars!]