Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
It was back in 2005 that I last tried BitDefender for Linux; it worked quite well as a command-line program, but had no GUI. Back then it was distributed as a .deb or .rpm package for easy installation. These days it's distributed as a .run archive, and it was fortunate that I had stumbled across the article "The 4 Best Free Linux Anti-Virus Programs", as it saved me reading the PDF for installation instructions.
Step 1. Request a free personal-use license from this page. This license is good for one year; you can get a new license when it expires.
Step 2. The email you receive will contain a download URL. In my case I needed to navigate to the EN_FR_BR_RO directory, then the Linux directory, then I downloaded BitDefender-Antivirus-Scanner-7.6-4.linux-gcc4x.i586.deb.run.