In beSOURCE, a "project" is a number of source code files you want to scan at a time. A project can be made of one or many source code files depending on your requirements.
Each project allows you to add as many source code files as desired, but once the project is being scanned (that includes all the source code files that were uploaded locally or from FTP, SVN, CVS, GIT, TFS), it is considered closed and you can't add any other source code files that project.