I whole paragraph in, and I -- a programmer, who has worked with text-to-speech APIs AND Python for years-- still don't know what the duck this is.

Imagine the average programmer or layman.

"Mycroft Core is a lightweight, portable piece of software written in Python."

Wrong. I don't care what language it's written in, nor whether it's lightweight or portable, until I know what it is.

Better: "Mycroft Core is an XXX. It is portable and lightweight piece of software written in Python"