Well this is part of the question.

That said, the protocol in this context is how computers "speak Bitcoin' with each other. This inciudes Bitcoin's consensus rules, most notably: what makes a Bitcoin block valid. But there are other important protocol rules as well, like how transactions are sent over the network.

Basic maintance I would define as making sure the software keeps running. So this can include bug fixes, making sure the code remains compatible with other programs, etc.

This stuff isn't always black-and-white though, and to me it remains rather unclear where Saylor actually wants to draw the line in this regard. (I'd say the general sentiment of the interview however pretty strongly suggests a "just don't touch it" attitude.)