For a lot of large open source projects, funding may come in the form of companies paying their engineers to dedicate a significant amount of their time to work

For a lot of large open source projects, funding may come in the form of companies paying their engineers to dedicate a significant amount of their time to working on existing open source projects. Or even open source projects that are part of a company's "products" (e.g. https://facebook.github.io/react/ https://facebook.github.io/react/ , http://llvm.org/ http://llvm.org/ ). Plenty of startups that use open source spend time improving open source projects (although, naturally, focused on the features they care to use, given how precious of a resource developer time is for a startup).