Distribution would be by email or by download. I currently get emails about HTML5 games I can download for my site. I haven't verified it but I assume they have some protection to keep people from easily changing the assets.
In the past I've distributed my games via flashgamedistribution.com and also by making games available via downloads from my sites. Again, I'm not looking for any heavy-duty copy protection just something to make it not quite so easy to replace/remove certain images.
Thanks!