A security-oriented operating system (OS).

Intended to be a basic example of an assembler for two simple architectures, written with the aid of lex and yacc (or GNU flex/bison). Being small, it should lend itself to learning, extension and modification. The source code is released under the GPL and has been built and tested on NetBSD, Linux and OS X.

Logic simulator with graphical entry, written in C# and released under the GPL.
Work in progress, a followup of http://www.cburch.com/logisim/, which is written in Java.

Cryptocat is free software with a simple mission: everyone should be able to chat with their friends in privacy.

   Open source. All Cryptocat software is published transparently.
   Encrypted by default. Every message is encrypted, always.
   Forward secure. Chats are safe even if your keys are stolen.
   Multiple devices. Devices receive messages even when offline.
   File sharing. Securely share files with friends.

Available for Windows, Linux and Mac.

WaveDrom draws your Timing Diagram or Waveform from simple textual description.
It comes with description language, rendering engine and the editor.
WaveDrom editor works in the browser or can be installed on your system.
Rendering engine can be embeded into any webpage.

Free real-time operating system for embedded systems. Can run with 1.5 kB of RAM and 5 kB of ROM. Native ports are available for OS X and Linux.

spigot is a calculating program. It supports the usual arithmetic operations, square and cube roots, trigonometric and exponential functions, and a few other special functions such as erf.

spigot differs from the average calculating program in that it is an exact real calculator. This means that it does not suffer from rounding errors; in principle, it can keep generating more and more digits of the number you asked for until it runs out of memory.

In particular, if you ask for a complex expression such as sin(sqrt(pi)), then most calculating systems would compute first pi, then sqrt(pi) and finally sin(sqrt(pi)), accumulating a rounding error at each step, so that the final result had a build-up of error and you would have to do some additional error analysis to decide how much of the output you could trust.

spigot, on the other hand, does not output any digit until it is sure that digit is correct, so if you ask for (say) 100 digits of sin(sqrt(pi)) then you can be sure they are the right 100 digits.

sshguard protects hosts from brute-force attacks against SSH and other services. It aggregates system logs and blocks repeat offenders using one of several firewall backends, including iptables, ipfw, and pf.

Free add-ons for Firefox and Chrome to help translating between chinese or japanese and english.

darktable is an open source photography workflow application and raw developer. A virtual lighttable and darkroom for photographers. It manages your digital negatives in a database, lets you view them through a zoomable lighttable and enables you to develop raw images and enhance them.

Available for Linux, FreeBSD and OS X.