While you need not be a member of ISI to submit a paper and have it reviewed, you agree to either become an ISI member or to pay an article publication fee if your paper is accepted for publication.

Our journals do not charge a submission fee. ISI members publish their works without a publication fee. There is an article publication charge (APC) for those non-ISI members who have only a free ISI colleague account. No APC is one of the many benefits of ISI membership.  See https://www.informingscience.org/Account/SignUp 

Non-members who prefer not to become members can pay the small APC. Currently this fee if $75 USD, which is the same amount as membership. We offer this option because some authors’ institutions will pay an APC for them, but not a membership fee.

The fees enable ISI to provide readers with free access to papers. ISI is a truly scientific organization, not a commercial enterprise masquerading as a professional organization. We believe in the free dissemination of high-quality research. The modest membership (and APC) fees provide the funding needed to pay the bills incurred in running an open-access journal.