RSA SecurID Software Tokens is described as ': Make strong authentication a convenient part of doing business. Deploy RSA software tokens on mobile devices—smartphones, tablets, and PCs— and transform them into intelligent security tokens'. There are four alternatives to RSA SecurID Software Tokens for a variety of platforms, including Linux, Mac, Windows, Android and iPhone. The best alternative is privacyIDEA, which is both free and Open Source. Other great apps like RSA SecurID Software Tokens are OnlyKey (Paid, Open Source), WiKID Strong Authentication (Paid) and stoken (Free, Open Source).
privacyIDEA is a modular authentication server that can be used to enhance the security of your existing applications like local login, VPN, remote access, SSH connections, access to web sites or web portals with two factor authentication.
OnlyKey is an open source alternative to YubiKey. OnlyKey natively supports: a hardware password manager, multiple two-factor methods (FIDO2, TOTP, and Yubico® OTP), passwordless SSH login, and OpenPGP.