Some top alternatives to Keybase includes Encrypt.me, 1Password, SendSafely, VoltShare and SmartEncrypt.
Yes, Keybase provides API.
Yes, Keybase provides a mobile app.
Keybase is located in New York, New York
Keybase offers One-time license, Quotation Based pricing models
The starting price is not disclosed by Keybase. You can visit Keybase pricing page to get the latest pricing.