There is a style of software distribution which is called postcardware or in short: cardware. It basically offers software for free when you send an old-fashioned postcard to the programmer.
I do like this idea although I stick to classic open source license models like the GPL. Therefore, I added a paragraph to the README files of my open source projects:
How to Thank Me:
I'm glad you like my tools. If you want to support me:
- Send old-fashioned postcard per snailmail - I love personal feedback! - see my address - [...]
This week, I got my first postcard!
It was sent by Jack Baty who also wrote a cool article on filetags and related tools by me. He is also using Memacs.
What a nice thing to do - it totally made my day.
To the surprise of many people who ask me about it, I hardly get any feedback at all on my software projects. So if you are out there, using nice open source tools, think about sending a postcard to the programmer or the project - it values the work invested for making those tools usable to others.