Good list. Sometimes the easiest way to contribute is to just donate some money, so that the existing maintainers can continue to focus on their work. OpenBSD is the "mothership" project for both OpenSSH and LibreSSL: https://www.openbsd.org/donations.html

Unfortunately I couldn't find any information on how to donate to these projects:

- https://re2c.org

- https://github.com/libexpat/libexpat

- https://github.com/linux-pam/linux-pam

- https://zlib.net

tzdata is actually maintained by IANA:

- https://www.iana.org/time-zones