Of course, you can do it. You just need download Sitebuilder 2.1 version from SWsoft site and accomplish upgrade. I suggest you to follow release notes during upgrade and don't forget to make copy of Sitebuilder database on your server and Sitebuilder working directory. Release notes you can find on the same SWsoft site. Here is a link: http://download1.sw-soft.com/SiteBuilder/2.1.0/Sitebuilder-2.1.0-rh9.build050915.20.txt
Prior to upgrading SiteBuilder version 1.x to version 2.1.0 it is necessary to make a back up copy of the folder: "/usr/local/sitebuilder"
and the database used by SiteBuilder.