FRK-Chess is designed as an easy-to-use system for playing chess games online without the need to sign-up for an account.
The game is played by two players over the internet. Players share a unique URL with each other, then take turns making moves at their own pace.
There are no accounts to sign up for and no confirmation emails (unless you want them). Just click new game and send your opponent the link.
To get started just click "Start New Game"
News! FRK-Chess goes open-source
I have released the code publicly on bitbucket, available here. The code is released under the GPLv3. Basically, you are free to distribute, modify, and use the software in any form, so long as you give others those same rights and include the GPLv3.