Beginning a new maintenance project is very disorienting. You're sitting there among a large set of files, of indeterminate quality and purpose. The previous maintainers may have left breadcrumbs in the form of documentation, executable software, and builder tool files, not to mention brain dumps from the rest of the (possibly departing) previous maintenance team. Or they may not, in which case you'll have to figure out how to build and run the thing yourself.
We still haven't discussed how to go about exploring the source code to find out how to start your own development, but that's a discussion for another column.