How can I easily determine a project's dependencies' licenses? For example on my GitHub repo which includes multiple open source softwares.
In case you are using java project build by maven than add https://github.com/openCage/loracle-maven-plugin into your pom.xml.
It checks whether all licenses of all dependencies (direct and transitive) are declared and fit together with your declared license.
note: my project
The OSS Review Toolkit's analyzer is designed to do just that. You need to clone your GitHub repo to a local working directory, and then run the analyzer on it as explained in the getting started document at the example of the mime-types project.
Disclaimer: I'm the founder and lead developer of the OSS Review Toolkit (ORT).