Open source games do exist, and the development scene is active and creative. You can get a taste of this by visiting sites devoted to Linux gaming, such as The Linux Game Tome, which highlights updated open source game projects every day. You can usually find a couple of announcements for new open source game projects every week.
However, most of these, despite often being based on innovative, interesting ideas and concepts, are disappointing hobby projects that lack a polished, solid user experience -- for several reasons.
First, compare the contributor list of an open source game you like to that of an open source utility you use. You will notice that games are often one-man projects. Developers rarely join forces and collaborate with existing projects. The momentum, collaboration, and synergy which characterize successful open source utilities is rarely achieved with an open source game.
Game development is a creative, funny, and extremely rewarding task at first. But before you can release a product, you must devote a huge effort to features that are not necessarily gameplay-related, but which are still important in the user experience. This includes menus, options, graphics, robustness, performance optimization, levels, the storyline, gameplay tuning, and more.
Good games not only need outstanding programmers, they also require graphic artists, animators, usability experts, musicians, and creators of sound effects. Most projects lack these contributors, and this is often apparent.
Countermeasures and perspectives
The Linux Game Tome's Game of the Month (GotM) project is an attempt to address this situation. Periodically, members choose a promising game project, and many developers join forces and merge competencies to polish the game and fix the most apparent defects to make it more usable and enjoyable. This is an intelligent approach to the problem, and has achieved important results so far. The Linux Game Tome also hosts a forum where game developers can discuss common problems and look for help from other developers.
The popularity of the Creative Commons (CC) phenomenon, which applies the philosophy behind open source software to other media, has created a wealth of quality content that open source game authors can freely use, although with some limits, depending on the specific license involved. This combination has not yet lived up to its potential, but eventually CC content creators, game developers, and users will benefit greatly. Just think of a driving simulator featuring a car stereo that plays music under a CC license, which gives the artists due credit and exposure. Who wouldn't love this?
Fun and simplicity?
That is not to say that all open source games are bad. A steadily (albeit slowly) increasing number of projects are mature enough to be enjoyed by many users, and be included in Linux distributions. For example, Foobillard, Armagetron, Chromium B.S.U., and Frozen Bubble are excellent open source games.
If you look for a common trait in these projects, you will find that they are usually limited in scope, without huge storylines, detailed scenery, or too many characters. In short, they are a long way from the complexity of current commercial offerings. Still, these simple but polished and well-implemented gems are a pleasure to play, thanks in part to their simple yet elegant graphics and solid, consistent gameplay.
Innovation, originality, and some examples
One of the advantages of open source is that innovation and creativity are free to emerge, whereas commercial settings often settle to safer, conservative concepts. This is especially true for modes of gameplay, where there is room for innovation that does not require huge effort from the development point of view.
Kenta Cho's games are a good example. Cho's games are written for Windows, but they are open source and use standard libraries like OpenGL and SDL, so many of them have been ported to Linux as well. They feature beautiful abstract and stylized graphics, characterized by fluid and elegant animation. Cho's games explore well-thought-out, balanced gameplay innovations.
For example, Gunroar is in many ways a standard, vertical scrolling shooter, but it implements an original scoring mechanism, where destroying an enemy instantly adds its bullets that are flying toward you to your score. Moreover, it offers several control modes: have you ever tried to control two ships at the same time? Many more original features are present in the game, and most of them heavily influence gameplay. For example, most ships (not only level bosses) have vulnerable parts, and the game difficulty is dynamically adjusted based on how you are progressing.
TUMIKI Fighters is another Cho game, and is even more imaginative and original. TUMIKI is a side-scroller shooter where the blocks you manage to detach from your toy-construction-like enemies stick to your ship if you fly over them while they are falling. The result is a weird-looking mass of incoherently-oriented blocks, which you try to grow as much as possible in order to gain shielding and fire power to defeat the level boss.
A7Xpg and its Linux port, on the other hand, have extremely simple Pac-Man-like game mechanics, but an incredibly deep gameplay which requires fast reflexes and experience: for example, points depend on the speed of the ship when it touches the golds -- but controlling the ship's speed is not simple at all.
In addition to Cho's games, you can find a number of other open source gems. For instance, Neverball and Neverputt focus on realistic physics and nice graphics, and are extremely enjoyable. Neverball is about tilting a floor with many obstacles in order to roll a sphere to a goal, while Neverputt is a miniature golf simulation. They share the same excellent game engine and graphics, but are totally different games from the player's point of view. They also feature an online hall of fame with replays, which is very active and conveys the success of the project.
We really hope that developer talent, creativity and cooperation, in synergy with Creative Common content, will help open source game developers to continuously improve their programs' quality.