The global economy’s digital infrastructure is based on free and open source software. To analyse how firms indirectly collaborate via employee contributions to developer-run projects, we propose a formal definition of ‘industrial public goods’ – inter-firm cooperation, volunteer and paid labour overlap, and participation inequality. We verify its empirical robustness by collecting networks of commits made by firm employees to active GitHub software repositories. Despite paid workers making more contributions, volunteers play a significant role. We find which firms contribute most, which projects benefit from firm investments, and identify distinct ‘contribution territories’ since the two central firms never co-contribute to top-20 repositories. We highlight the challenge posed by ‘Big Tech’ to the non-rival status of industrial public goods, thanks to cloud-based systems which resist sharing, and suggest there may be ‘contribution deserts’ neglected by large information technology firms, despite their importance for the open source ecosystem’s sustainability and diversity.