[okfn-discuss] doi equivalent?

[graham]

Hi,

I'm new to this list so this may be a faq - if so please point me in the 
right direction!

Is there any free equivalent to the DOI naming system (http://doi.org/) ?

I'm looking for something to generate unique ids for a potentially large 
set of publications in .epub format. I'd like something which would let 
them be part of a larger ecology when released (as with doi numbers) but 
which doesn't cost money (don't have any) and isn't a proprietary system 
(not certain about doi - it's certainly copyrighted and trademarked)

Thanks
Graham