Pencil2D It lets you create traditional hand-drawn animation (cartoon) using both bitmap and vector graphics.

The basic features of Pencil2D are:
+ layers support (separated layer for bitmap, vector and soud part)
+ bitmap drawing
+ vector drawing
+ sound support

Vym (View Your Mind) is a mind diagramming program. It is useful for organizing thoughts and working on structuring something.
A connection diagram (mind map, mindmap) is a color radial diagram with an image in the center, illustrating semantic and other connections between parts of scientific material.
For example, it can graphically illustrate the structure of a dissertation plan, a project plan, or the structure of government institutions in an area.
Communication diagrams have many applications in personal, family, educational, and business situations.
Opportunities include note-taking, brainstorming, summarizing, revising, and general clarification of thoughts.

BRL-CAD is a powerful cross-platform Open Source combinatorial Constructive Solid Geometry (CSG) solid modeling system that includes interactive 3D solid geometry editing, high-performance ray-tracing support for rendering and geometric analysis, network-distributed framebuffer support, image and signal-processing tools, path-tracing and photon mapping support for realistic image synthesis, a system performance analysis benchmark suite, an embedded scripting interface, and libraries for robust high-performance geometric representation and analysis.

Scribus is an application for professional visual layout of printed documents (newspapers, magazines, brochures, literature, etc.) capable of creating high-quality pages for any purpose - be it replication for printing or electronic distribution.
Scribus supports all the features of professional publishing systems, such as extensive capabilities for layout and pre-press preparation of text, the CMYK color model, Spot Colors, the ICC color output management system, and the creation of PDF files.
This is similar to AdobeInDesign or QuarkXPress.

qCAD is a professional CAD system, similar to AutoCAD, designed for creating mechanical engineering drawings and architectural plans. You can create technical drawings such as building plans, interior plans, mechanical plans, or schematics.
You can also easily create and edit drawings with ISO templates and save files in DXF format. The DXF format is used by many CAD systems.

LibreCad - CAD for 2D drawing and design. Allows you to solve 2D design problems, such as preparing engineering and construction drawings, such as building plans, interior plans, machine parts or diagrams and diagrams.

KediCAD is a 2D analogue of AutoCAD.

This program has a simulation feature that allows you to make expected changes to general drawings.

KediCAD can also be used to create a drawing of the moment of inertial calculations and calculation of bends.

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Lazarus is an integrated cross-platform software development environment in a Delphi-like environment in the Object Pascal language for the Free Pascal Compiler (often abbreviated FPC).
It is currently the only Rapid Application Development (RAD) tool that allows Delphi programmers to create GUI applications for Linux (and other non-Windows) systems.
Allows you to easily transfer Delphi programs with a graphical interface to various operating systems: Linux, FreeBSD, Mac OS X, Microsoft Windows, Android.

FreeCAD is an extensible CAD/CAM system that includes some key concepts such as macro recording, workspaces, the ability to run as a server, and dynamically loaded application extensions.

FreeCAD can import and display CAD models in IGES, STEP and BRep formats, as well as meshes in STL, BMS, AST and Wavefront OBJ formats.

KDevelop is a free integrated development environment (IDE). There is source code navigation and debugging for projects in different programming languages, work with different build and version control systems, and all this is implemented on a modular basis.

KDevelop can analyze code in C, C++ and Javascript/QML, and there are also external modules for PHP and Python.