Roguelike games are usually freeware: free to play for as long as you like. A small handful might now or in the future be shareware, where you pay if you exceed a certain evaluation period; and a couple are moving in the direction of being fully commercial, where you have to pay to get full game, although a reduced demo might be free. Freeware by far dominates the Roguelike genre.
In addition to being free to play, many Roguelikes, particularly those with "ancient" heritages such as Angband and NetHack, are free to modify and distribute. Many of the newer Roguelikes become "open source," if not immediately, then over time once the author is either satisfied with the stability and quality or unable to continue further development himself.
In most cases, once a game is declared "free", all its subsequent variants have to be free. This is usually passed on as a written requirement in the distribution.
Below is some concrete information as to executable and source availability. I don't intend it to be exhaustive, but big enough to give you a general impression. I'll update it when I get additional information:
|Adventurer of the Realm||1998||Free||Yes|
|ADOM Deluxe||future||$20 shareware||Probably not|
|ADOM II (JADE)||future||Free||Yes|
|Dungeons of Des Moines||future||Free||?|
|Hack (and descendents)||1984||Free||Yes|
|Lord of Rage and Death||1998||Free||No|
|Post Nuclear Adventure||1998||?||No|
|Legend of Saladir||1997||?||No|
|Unreal World||1994||$25 shareware||No|
|War of the Runes||1998||Free||No|
The open source nature of Roguelikes has resulted in a plethora of variants, clones, utilities, spoilers, ports, and download sites. The sheer amount of variety and information can be overwhelming at first, and that's one of the reasons I created this web site... Not because I'm sadistic but because I thought I'd... uh... well, yeah, I guess there's no excuse! :)
Since it's awfully hard to support yourself off of freeware (yes, that was a joke), Roguelike developers have day jobs or are students. Also, they tend to work individually as opposed to in teams (coordination takes resources). This limits the pace of development (an upcoming topic in itself).
Because money is almost never in the picture, developers and players alike have nothing at risk. They are typically very friendly, accessible, intelligent, and genuinely helpful. There are of course exceptions (your usual immature hot heads or bored flamers), but for the most part, the Roguelike community is awesome.
Most of the side effects listed above will form upcoming topics in themselves.