Supporter is described as 'With Supporter you are able to support favorite open source projects and authors of free content' and is an website in the Development category. There are six alternatives to Supporter, not only websites but also apps for Self-Hosted solutions, Google Chrome, Bitcoin and Android. The best alternative is Open Collective, which is both free and Open Source. Other great sites and apps similar to Supporter are Flattr (Paid), Tipeee (Free), Tip4Commit (Free, Open Source) and CommitChange (Free, Open Source).
Flattr is a social micropayment service, that makes it easy for you to "flatter" things on the internet that you like. When you're registered to Flattr, you pay a small monthly fee of your own choosing.
Contribute to Open Source, donate bitcoins to open source projects or make commits and get tips for it. How does it work? People donate bitcoins to projects. When someone's commit is accepted into the project repository, we automatically tip the author.