Off course you can. For example, download the bundles you want from the internet and copy them on your HPUX server, then you can perform a manual installation using osgi:install command with the file URL handler.
Look here for details:
and here for File URL handler:
You can also copy a maven repository already populated with the required artifacts on your server and then use osgi:install command with the mvn URL handler (http://fusesource.com/docs/esb/4.2/deploy_osgi/UrlHandlers-Maven.html).