This artifact originates from the Orbit Project at Eclipse, it is an osgi bundle and is signed as well.
'org.eclipse.jetty.orbit:javax.activation:1.1.0.v201105071233'
<dependency>
<groupId>org.eclipse.jetty.orbit</groupId>
<artifactId>javax.activation</artifactId>
<version>1.1.0.v201105071233</version>
</dependency>
<dependency org="org.eclipse.jetty.orbit" name="javax.activation" rev="1.1.0.v201105071233"/>
"org.eclipse.jetty.orbit", "javax.activation", "1.1.0.v201105071233"