Livius.org is a not-for-profit project and will always be free. If you want to take a share in the costs, you can donate money to the Stichting Wetenschapsvoorlichting Oudheid, a small philanthropic foundation that supports the improvement of science/scholarship education. It has in the past supported Livius.org and several other projects.
Stichting Wetenschapsvoorlichting Oudheid
The Hague, The Netherlands
The account number is IBAN NL25 INGB 0006 2904 08; BIC/SWIFT INGBNL2A.
Thank you very much.