SVN stands for the Subversion is an open source version control system. This is code database repository that is developed with all copies of all code that has been checked in by developers. With a system like this you could go back and check out any previous version of the the software.
The open HPSDR project maintains a SVN for the the members of the project. The top address of the repository is:
Web browser usually do not browser subversion repositories. You will need some SVN software to access the repository. The names and types of software vary by your operating system.
Code is not generally erased from a repository. So many of the some of the directories are very active and may change daily other may have not changes in years. Check the dates on the files to determine when tey were lats updated. Your SVN program will help you keep a up to date copy o the code on your computer and you can easily update the directory with a single command.
The repository evolves over time so the organization is not usually for the new viewer but for those that post code. to help people find things here is a index major folders.