You need to use the JMS tools and ask to install it in the slave site.
I have do it and it works.
In JMS 1.2.x, you have a menu called "Tools".
There you can supervise the installation of all the extensions.
So you can select the website where you want to install an extension and just click "install".
If you are still using a JMS 1.1.x, this will be more difficult to re-install any "NoNumber" extension due to their specific (experiment) installation processing.
This is the same problem than "Content Templater" that is distributed by "No Number".
See
www.jms2win.com/forum?func=view&id=582&catid=3