If you intend to distribute ePubs, for free or otherwise, you need to make sure you have permission from the font's copyright holder before embedding them.
Just having bought a user licence isn't enough, nor are fonts that come with your operating system necessarily free for distribution in ePubs.
So - you need to make sure you have permission to distribute the fonts.
If you have blanket permission to distribute, you don't need to encrypt them. But for most fonts, you're more likely to get permission to embed the fonts in distributable documents, but not to redistribute the fonts themselves. Since ePubs are essentially zip files, embedding fonts is ePubs without encryption is probably considered redistribution, not embedding, since they can be extracted so easily.
So. You'll need to encrypt the fonts you embed in ePubs. Unfortunately, there are two methods of doing that. The Adobe method, which is supported by ADE and all ebook readers that include ADE, and the standard IDPF method, that no reader currently supports. So at the moment, my script uses the Adobe encryption method.
ePub is a remarkably new format, and being standards based, change is slow, as there's no one person that can dictate changes. Also, the readers and tools are slow to appear, which si why I needed to roll my own font encryption script.
Originally Posted by ghostyjack
I'm not very familier with the SVG code, but a bit of experimentation should help me understand how to use it for my covers.
I'm not sure I understand the need to encrypt fonts. I take it this would be only neccessary if it is for a font that isn't free or comes supplied with the OS? Or is it neccessary for me to do this for all fonts I use?
I thought my second question may be difficult, any help on that one would be great.