It is code, so it is the most flexible that can exist. You can call the code with an application that includes it, you can make your own server with your own API although that isn't really useful if the server is going to be local anyway (most of these thing deal with private data, you don't want a central entity managing private data). You can call a process from another process, I don't see what's stopping you.

Perhaps if you have an example of what you want to build I can understand how woob doesn't fit what you want to do