Today we've announced that we've signed an agreement to acquire NPM but we technically have not acquired them yet (referred to as "closed"). NPM is still their own company for now and that's why the language is future tense.
I literally thought that, clicked hide, then thought "Wait a minute, do they mean...?" and had to go fish it out of hidden items.
"Joining" is an interesting term here... but I suppose it won because it sounds more like something friendly humans would do. "NPM Is Breaking Bread and Sharing with Github as Special Friends."