A variation of cardware, Emailware, uses the same approach but requires the user to send the author an email. An example for emailware is the videogame Jump 'n Bump. Postcardware, like other "novelty" software distribution terms, is often not strictly enforced.
Cardware is similar to beerware.
The concept was first used by Aaron Giles, author of JPEGView. Another well-known piece of postcardware is the roguelike game Ancient Domains of Mystery, whose author collects postcards from around the world. Orbitron is distributed as postcardware. Exifer is a popular application among digital photographers that is postcardware. Caledos Automatic Wallpaper Changer is a "still alive" project cardware. "Empathy" is a postcardware for password-protected executables. Dual Module Player and Linux were also postcardware for a long time as well.
- Jump 'n Bump readme.txt JUMP 'N BUMP by Brainchild Design in 1998 Jump 'n Bump is e-mailware. That means you're supposed to send us an e-mail. Write for example where you're from and what you thought about this game. If you do that, you will greatly encourage us to make more games for you!
- Giles, Aaron. "Aaron's Computing History". Retrieved 2006-08-07.
- Torvalds, Linus. Just for Fun. New York: HarperCollins Publishers. ISBN 0-06-662072-4.