The web tools on this site — ASN lookup, VPN/proxy/datacenter detection, reverse DNS, IP geolocation — are free and always will be. Several users have asked for the same data as an API.
We haven't built it yet. If an API would be useful to you, leave your email and a line about your use case — volume, endpoints, whether you need bulk lookups. If there's enough demand, early respondents get free access first.