https://github.com/stapler/stapler/commit/fef6e6151f5122bafd44dba24409778038b4c539 (or an earlier commit) is responsible: !hasAllowedExtension("/META-INF/licenses.xml") so resolveScript returns null.

Code changed in jenkins
User: Jesse Glick
Path:
changelog.html
core/src/main/java/hudson/AboutJenkins.java
core/src/main/resources/hudson/AboutJenkins/index.jelly
http://jenkins-ci.org/commit/jenkins/0bf434845b5de755d730fb73ae1688b02dba8894
Log:
[FIXED JENKINS-17724] /about was not showing licenses.
A recent Stapler update caused the Jelly facet to ignore *.xml.
So need to use raw j:include (as plugins were doing), not st:include (as core did).

Integrated in jenkins_main_trunk #2486
[FIXED JENKINS-17724] /about was not showing licenses. (Revision 0bf434845b5de755d730fb73ae1688b02dba8894)

Result = SUCCESS
Jesse Glick : 0bf434845b5de755d730fb73ae1688b02dba8894
Files :

• changelog.html
• core/src/main/resources/hudson/AboutJenkins/index.jelly
• core/src/main/java/hudson/AboutJenkins.java

Code changed in jenkins
User: Jesse Glick
Path:
changelog.html
core/src/main/java/hudson/AboutJenkins.java
core/src/main/resources/hudson/AboutJenkins/index.jelly
http://jenkins-ci.org/commit/jenkins/45699fed47c0b1f1154296d7cba44c852b7df3d1
Log:
[FIXED JENKINS-17724] /about was not showing licenses.
A recent Stapler update caused the Jelly facet to ignore *.xml.
So need to use raw j:include (as plugins were doing), not st:include (as core did).(cherry picked from commit 0bf434845b5de755d730fb73ae1688b02dba8894)

Conflicts:
changelog.html
core/src/main/resources/hudson/AboutJenkins/index.jelly