I have zero empirical data to back it up but as a freelance I.T. consultant, my gut instinct is that part of the trend (at least within the realm of I.T. infrastructure/security/management that I am most familiar with) has to do with increasing development of derivatives from other OSS projects, which generally involves adoption of the parent project’s license, in whole or in part, so there’s a function of OSS spawning more OSS.
It could be an interesting data analysis project to work out some mechanism for establishing OSS “family trees”.