Flattr is a system of micropayment allowing everyone to remunerate the author of a publication.
The way it works is a bit particular since you pay a fixed amount each month and this amount of money is shared between all the publications you flattred. For example i give 2€ monthly and i flattted 5 times Bob, 3 times John and once Bill and Roger. We have a total of 10 actions, which means 20¢ by action, Bob will earn 1€, John 60¢ and Bill and Roger 20¢ each. The fact is that Flattr for paying its infrastructure and people take 10% of your fees, so to have the right bill i should have given 2,22€ a month. This might be better explain on their website.
Because it allows you remunerate authors of whatever in a symbolic but real way. Every author of a publication, a text, a music or a movie takes time to do it, often on his free time. For my purpose my work pay me sufficiently to allow me to pay the server on which this site is but for many other creators like artists, it allow a remuneration without working with majors.
I really don't know. For France i will ask them once the declaration of incomes will be over. If you have information on how it works in your country feel free to let a comment, i'll update.
I create a flattr block for concrete5. It's available for download there: https://github.com/gaetronik/Concrete-5-Flattr. You only have to decompress or clone the git repository in the blocks directory of your concrete5 root directory. Then in the dashboard of concrete5 the flattr block appears as available for installation in the add functionality section. One click on install and you can insert a flattr block on your page.
You just have to add a Flattr block on your page and fill the pre-filled form. After you save the page it will be shown.
It's easy, the code is available on github. I will merge the modifications you made after a code review.
Have a good Flattring!