In this paper, we examine the motivations of large information technology ("IT") vendors, to invest in open source software ("OSS"). What drives companies with large, proprietary software portfolios to invest hundreds of millions of dollars in OSS? We approach this question by grouping a sample of OSS projects into clusters and examining vendors' motivations for each cluster. We find one cluster has received almost no investment. Contributions to projects in this cluster are confined to the voluntary effort of the vendors' employees, and vendors are likely altruistically motivated. By contrast, the other cluster has received over 99% of vendor investments. Here, vendors are more likely economically motivated to invest in OSS projects that can serve as a complementary asset to vendors' core, proprietary businesses.