It’s true that Android is open source software, but it’s also the case that if you manufacture handsets and you’d like to run it as your operating system, there are rules (and now, even more than there were in the past).
You must include the search bar positioned near the top of your display (currently on the home screen, though it may also become a requirement for every screen) and Google’s apps must be featured in a place of prominence (hence the Google folder of apps).
Those that scowl at Apple for similar practices will not be thrilled to learn that these apps cannot be deleted from your device (well, not easily anyway). There are currently 9 apps that are required, but moving forward there could be any number more that Google deems necessary for you to have (even though most Android users don’t use them at all).
Is this move wise for Google? Having stricter controls is certainly a good thing if Android wants to break into enterprise and corporate markets that require a more structured and reliable approach to software, but it also risks alienating the control-hungry, tech-savvy, crowd that has made the platform a success.