KoLmafia is a cross-platform desktop tool, written in Java (J2SE 1.5 compliant), which interfaces with the online adventure game, Kingdom of Loathing. Those who are looking to download the latest release: click here. More advanced users familiar with stand-alone Java applications are welcome to download an hourly build provided by the KoLmafia user script community: click here.
To make things absolutely clear, open sourcing a program does not make it secure -- it strictly makes it easier to take advantage of work already done by other people, provided you are willing to act in accordance with the terms of the license under which the source code is provided. That said, I believe KoLmafia is safe. However, I'm the main developer of KoLmafia, and I only use a small fraction of its features, so my opinion of it should be taken with a grain of salt.
My personal belief is that running any program (including the web browser you are using to view this page) is about near-unconditional trust. If, for any reason, you don't trust the companies and individuals involved in the development of the program, I strongly suggest that you should never run the program, no matter what the promised benefits may be. I believe these same guidelines should be applied if you're thinking about using KoLmafia.
In order to use KoLmafia, you (usually) must have a Java Runtime Environment (JRE) installed for your system.
If you are running Windows 2000/XP, Linux, or Solaris, you can use the version of Java provided by Oracle, usually referred to as the Sun JRE or the Oracle JRE. The latest version of the JRE is available here: Java SE Downloads. Please be sure to install the JRE after downloading it!
Uniquely to Windows, you can try running KoLmafia without Java at all by using a solution that tries to convert KoLmafia to native code. In theory, this makes everything faster as the code is no longer interpreted and may perform better in terms of memory usage. The solution is provided by leveraging a commercial Java to native code compiler called Excelsior JET, which is generously made available by the vendor at no cost for non-commercial use. The badge below is a small show of thanks for their generosity.
If you are running Mac OS X 10.4.x or higher, you do not need to download or install a separate JRE. If you are running an older version of Mac OS, unfortunately, KoLmafia will likely not run on your system because Java versions higher than Java 1.5 are not maintained for those versions of the Macintosh operating system.
If you are using any operating system not listed here, you are welcome to try your favorite search engine for details. The applicable keywords are "Java 1.5" or "Java 5.0" (they are synonymous) and the name of your operating system, though you may have more luck searching for "Java 1.6" (which is more generally known as Java 6).