2.14 - Unexpected servlet-api classes on plugin test classpath

Some additional details:

Looking through the contents of

~/.gradle/caches/2.14/generated-gradle-jars/gradle-api-2.14.jar

there are a number of different libraries embedded in there:

aQute
com/amazonaws/regions
com/amazonaws/services
fr/jayasoft/ivy
javax/servlet/jsp
javax/servlet/resources
jcifs/http/ne.css
jcifs/util/mime.map
net/rubygrapefruit/platform
org/apache/ivy
org/apache/maven
org/apache/tools
org/apache/xml
org/eclipse/jdt
org/joda/time
org/mortbay/jetty
org/mortbay/xml

Q, Does this mean that gradle plugins are limited to use only the versions of these supplied libraries?