Download of OTPPassword 2.3 for Mac was available from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this free Mac application is App System Code. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. OTPPassword for Mac lies within Security Tools, more precisely Personal Security.
From the developer:
Mobile OTP Authenticator is a two-factor authentication OTP application. The utility supports all services that provide time-based authentication using HOTP and TOTP algorithms. You can manually set up the account. The account is stored in data security in the iCloud key holder.
You may want to check out more Mac applications, such as Secret Folders, Ghost or Keychain Minder, which might be similar to OTPPassword.