Yeah, according to the Contributing.md on the github it is missing some files that are included if you buy a copy of the game:

The BarotraumaShared/Content folder, which contains Barotrauma’s art, item XMLs, sounds, and other assets, is not included in the GitHub repository. If you have a legal copy of the game, you can copy the Content folder from the game’s files to BarotraumaShared/Content.