OpenSSH / OpenBSD
What is OpenSSH?
OpenSSH is a FREE version of the SSH connectivity tools that technical users of the Internet rely on. The OpenSSH suite replaces rlogin and telnet with the ssh program, rcp with scp, and ftp with sftp. Also included is sshd (the server side of the package), and the other utilities like ssh-add, ssh-agent, ssh-keysign, ssh-keyscan, ssh-keygen and sftp-server.
If you use the SSH protocol to connect to a server from Windows, Linux, Mac, ... you are probably using OpenSSH.
What is OpenBSD?
The OpenBSD project produces a FREE, multi-platform 4.4BSD-based UNIX-like operating system. Efforts by OpenBSD influence a lot of the software world. OpenBSD was the first to provide anonymous access to their source code. Secure C functions like strlcat(), strlcpy(), arc4random() and bcrypt() come from OpenBSD. Android uses OpenBSD's libc. OpenBSD has a strong focus on security and a lot of exploit mitigation techniques were first introduced and turned on by default on OpenBSD. They are one of the first to have 64-bit long long time_t and use it to help other software to overcome the year 2038 problem. OpenBSD's pf firewall is used in FreeBSD, Mac, QNX, Solaris 12. They were the first to have full IPv6 support and tools like sudo and tmux come from OpenBSD.
I am not mentioning a lot of other things but the baseline is that they do a lot of good work, you should donate.
How to support
OpenSSH is developed by the OpenBSD Project. The software is developed in countries that permit cryptography export and is freely useable and re-useable by everyone under a BSD license.
However, development has costs, so if you find OpenSSH useful (particularly if you use it in a commercial system that is distributed) please consider donating to help fund the project.