Some of my project's dependencies have scope=system and thus, having systemPath element.

<dependency>
<groupId>thumbnailator</groupId>
<artifactId>thumbnailator</artifactId>
<version>0.4.0</version>
<scope>system</scope>
<systemPath>${basedir}/src/main/webapp/WEB-INF/lib/Thumbnailator-0.4.0.jar</systemPath>
</dependency>

However when doing 'project add-dependency' with Forge, it removes the systemPath so the project doesn't build anymore.