Kernel Mode Linux is a technology which enables the execution of user programs in a kernel mode. In Kernel Mode Linux, user programs can access kernel address space directly. Unlike kernel modules, user programs are executed as ordinary processes (except for their privilege level), so scheduling and paging are performed as usual. Although it seems dangerous, the safety of the kernel can be ensured through such methods as static type checking, software fault isolation, and so forth.
Linux is a clone of the Unix kernel, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance. It has all the features you would expect in a modern fully-fledged Unix kernel, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and TCP/IP networking.
Visopsys is an alternative operating system for PC compatible computers. Under development since late 1997, this system is small, fast, and open source. It features a simple but functional graphical interface, real preemptive multitasking, and virtual memory. Though it attempts to be compatible in a number of ways, Visopsys is not a clone of any other operating system. You can demo the distribution from a "live" CD, USB stick, or floppy disk.
Astaro Portscan Detection is a netfilter target which will attempt to detect TCP and UDP port scans and log them to syslog. This target is based upon Solar Designer's scanlogd. It suppports mutliple levels of logging, custom prefixes for entries, weighted total port scan detection, and port scan temporal spread detection.