Open Design Alliance (ODA)
The Open Design Alliance (ODA) is a software consortium who have been at the forefront of challenging Autodesk dominance by providing compatibility with DWG files and more recently Autodesk Revit RFA/RVT files without an Autodesk license. They have a commercial IFC SDK solutions for integrating IFC based workflows into member software. Their solutions are proprietary, but they offer a few cost-neutral services. Their Drawings SDK (previously known as Teigha) supports .dwg and .dgn file formats.
They are a not-for-profit member owned consortium designed to avoid outside influence or over influence from any single member(s). In 2020 Autodesk became a member of ODA (to many peoples surprise). Among their members (2020 buildingSMART presentation) are Oracel, Nemetschek, esri, Autodesk, Leica, BricsCAD, Siemens, Trimble, Gräbert, Graphisoft, Bentley, Vectorworks, Dassault Systemes, DDS.
"The ODA Platform is a comprehensive solution for developing engineering applications, consisting of SDKs for popular CAD and BIM formats and the ODA Technology Stack, a set of building blocks for application development."
- LibreCAD is a free/libre alternative to AutoCAD
- QCAD is a free/libre alternative to AutoCAD
- BlenderBIM_Add-on is a free/libre alternative to Autodesk Revit
- FreeCAD is a free/libre alternative to Autodesk Revit
- online DWG/DXF converter https://www.opendesign.com/oda_online_converter
- cross platform DWG/DXF converter: https://www.opendesign.com/guestfiles/oda_file_converter
- ODAs DWG specification: https://www.opendesign.com/files/guestdownloads/OpenDesign_Specification_for_.dwg_files.pdf
- Free Windows only IFC viewer with BCF and (soon) MVDXML support https://openifcviewer.com/