Stratechery does a good job of distinguishing between a platform (often very closed) and an ecosystem (open source software):
I think there is an important distinction between platforms and ecosystems. While these words are often used interchangeably, I think of a platform as, well, a platform: something that is built upon. In the case of the iPhone, iOS is the platform on which apps are built. An ecosystem, on the other hand, suggests a more equitable relationship: different pieces that work together to mutual benefits.
This is why I love working with open source software, rather than app stores.