Not to detract the graveness of the situation in https://www.bellingcat.com/news/uk-and-europe/2019/04/19/an-open-source-survey-of-the-shooting-of-lyra-mckee/:
The use of the term "open source" instead of "collaborative" seems to imply being infected with the buzzword bug that's been going around.
The collaboration among the journalists and the law is recommendable. This is not open source. What would be is having a repository with all the input from the scene available for others to push to and draw data to compile stories.
Linux geeks doing what Linux geeks do...