I'm part of the editorial committee of a small open access ecology journal that is slowly growing Currently, our journal doesn't have the means to pay for the doi service, but we found this service which offers a different identifier, the EOI. We asked for additional information and some of the claims the state are:
"You will be eligible to get EOI for any number of papers for your publication."
"You need to pay one-time membership charges USD $100..."
"No charges per EOI."
"For DOI you need to pay USD $2 per DOI, which cost really high for journals and membership charges ranges from USD $300 to USD $100000."
"Both these objects serve the same purpose, but in EOI we provide more flexibility & tools will be provided periodically for submission, no charges for errors (will be corrected by Citefactor staff)"
They also list a sample of journals that use their service, which are not necessarily highly recognized, but then it would be also our case.
Is there any other alternative around to have a proper unique identifier for our articles?