Most free (libre) software is also gratis, but not all! Some free software costs money, but with it comes all of the freedoms to share with your neighbor and make modifications! Buying free software ensures that our traditions can continue, and donating to gratis projects does the same.
libre - gratis > gratis - libre
Fosstodon is a Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.