You can use it for a while, maybe a long while, without the source code. But if ...

You can use it for a while, maybe a long while, without the source code.

But if you have the source, you can keep it going forever, rebuild a community of committers, add bug fixes, security fixes, new features.

Move to new architectures, add new abstractions, build your business on it without worrying that someone will arbitrarily try to kill it off...