I meant more ancillary things like custom source control, custom testing frameworks, custom database, custom build tool, hand configured servers that only Alice

I meant more ancillary things like custom source control, custom testing frameworks, custom database, custom build tool, hand configured servers that only Alice knows how to provision, maybe even a home-grown programming language. Edit: Since the original article is about Google, I should perhaps clarify that Google is big enough that it can do get away with having all or some of the above. But they are wise to open source most such things, so that they ensure their versions stay competitive rather than becoming a drag.