The integrated user reference of the QCAD Community Edition is available as part of the QCAD sources at:
For example, the English documentation of the line from two points tool can be found at:
Line2P_desc_en.html contains a brief description (desc) of the tool in English (en)
Line2P_proc_en.html contains step by step instructions for the procedure (proc) to use the tool in English (en)
The format is simple HTML (without headers, footer). The manual is generated automatically from these files.
If you wish to contribute, please create a github account can then contact me so I can add you to the list of contributors. As a contributor, you can edit these files online or clone and commit / push using git.