this is the correct behaviour.

You need to either:
a) add the property to project.properties inside the plugin (not recommended)
b) put the property in ~/build.properties (affects all projects and plugins)
c) add the property to the command line with -D

What is your reason for doing this? If you are just manually downloading JARs, perhaps it is better to put them in the local repository directly?

regression

project.xml:
<dependency>
<id>commons-collections</id>
<version>???</version>
<properties>
<war.bundle>true</war.bundle>
</properties>
</dependency>

project.properties:
maven.jar.commons-logging = ${basedir}/lib/commons-logging.jar

I get this error because the plugin also tries to use it:

Het bouwen kan niet doorgaan, omdat de volgende afhankelijkheden niet achterhaald kunnen worden:

commons-logging-1.0.3.jar; path override doesn't exist: C:\Documents and Settings\Geoffrey\.maven\cache\maven-xdoc-plugin-1.8
\lib\commons-logging.jar

Due to legacy reasons it is not possible to use the repository for now for everything, although we understand it's better to use the repository.

a workaround is to call it
commons-logging-override

this way it's also flagged in the project.xml as evil

see MAVEN-1610 for a test case