Yes, but you'll need to be in keeping with the software license terms (that is, your site will either display PHP Fusion copyrights, or you will have to be able to provide proof of a paid license on demand) and the installation must come from an official source. (x10Hosting takes warez and copyright infringement very seriously, and anything uploaded containing the signatures of known warez groups will likely result in an immediate permanent suspension, even if you have a paid license.)