Hallo, it is possible, why not? Just place avast's library and binaries in the right directories (/usr/lib, /usr/bin, /etc) and that's all. The (BFU-friendly:) process of live-cd re-mastering usually consists of normal installation, adding packages, and then, compressing the whole thing to particular filesystem (usually squashfs, cramfs or compressed loop-device)...
Sorry, I was thinking about Windows version in a live CD. My fault.
Why don't you implement a bootable CD with avast for Linux then?
I'll tell you why: because Linux Distro packagers are so damned sure that:
1 Linux is not vulnerable ... (to most viruses affecting Windows I admit it's probably true)
remains about 50 viruses all in all that could affect Linux but are rarely met.
2 people dual-booting with Windows are not worth the integration of Avast in a distro...forgetting at the same time that an USB win32 formatted can be infected in Linux and infect your system when you reboot into Windows.
The Linux guys don't care. That's why they won't ever integrate an anti-virus on any live cd or any sort of Linux setup. It's a shame but it's like that. This said, they don't mind allowing Linux accessing NTFS partitions 
I have made one some time ago, but there's very low interest in such things (because, who would need it, is usually able to install avast in his own live-cd, it's the same as on any other linux. well, to have it on the cd directly needs a bit o re-mastering, but it involves just copying files to the ISO image, nothing more).
regards,
pc
