The Simpocalypse program itself was written by Peter Piwowarski for the Delta College STEM Explorer, but it depends on a lot of open-source software to work. We've tried to find everything that it uses and include the licensing terms here. All of these are permissive licenses, similar to the MIT or BSD licenses.

Tcl and Tk are absolutely essential to Simpocalypse, and it can't run without them. Tcl is a dynamic scripting language first designed in the late 1980s for controlling electronic design automation software, and Tk is a graphical widget toolkit designed to be controlled from Tcl, and first released in the early 1990s. All of Simpocalypse's source code is written in Tcl, and its graphical user interface is rendered entirely by Tk. They are governed by the folllowing licenses:

• Tcl's license.terms file
• Tk's license.terms file

Simpocalypse also relies on the SQLite relational database management system to manage its internal data structures, especially the ones that power its statistical history features. SQLite is public-domain software, meaning its authors have renounced any copyright interest in it. They do however distribute a "blessing" instead of a copyright license:

• SQLite's blessing

Additionally, certain other pieces of software are included with Simpocalypse for all platforms, either because its source code uses them or its single-executable runtimes use them. They are govened by these licenses, mostly very similar to Tcl's:

• Tcllib's license.terms file
• Metakit's license.terms file
• The Tclkit license.terms file
• The license from zlib's source code
• The splash screen uses the awdark Ttk theme. Its author has released it under the same license as zlib.

Finally, the Linux executable file includes various pieces of open-source library software to make sure it can run on as many Intel-compatible Linux systems as possible. Almost all Linux computers will already have copies of most of this software, but Simpocalypse comes with its own copies built in to make sure there can't be any weird compatibility problems, no matter what. The only one of these that your Linux system probably doesn't have already is the musl implementation of the C standard library. We use musl because it is better for distributing built in to things like Simpocalypse than the glibc C library that almost all desktop Linux systems come with. Most of the rest of these libraries are needed by Tk, to talk to the X Window System GUI framework traditionally used on Linux and other UNIX-like operating systems. Here are all of their licenses:

• bzip2's LICENSE file
• expat's COPYING file
• fontconfig's COPYING file
• FTL.TXT from FreeType
• The license for Theodore Tso's libuuid
• libX11's COPYING file
• libXau's COPYING file
• libXdmcp's COPYING file
• libXft's COPYING file
• libXrender's COPYING file
• musl's COPYRIGHT file
• libxcb's COPYING file