The executable of chaos is in the public domain and may be freely distributed. The source code, documentation, and levels are copyright Sean A. Irvine and may not be modified without the author's permission.
By paying a registration fee of $20 US (or the equivalent in some other useful currency) or $20 NZ (for a New Zealand address) you will receive the latest version of the game, well documented source code, and a level generator. Those who pay the registration will have a partial waiver of the source code copyright and will be permitted to alter the source code. Please make cheques payable to Sean Irvine. My address is given at the end of the instructions.
Chaos was written using SAS C on an Amiga 500 with 1MB of memory.