pybossa is described as 'PYBOSSA is the ultimate crowdsourcing framework to analyze or enrich data' and is an app in the Education & Reference category. There are five alternatives to pybossa for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and Android. The best alternative is BOINC, which is both free and Open Source. Other great apps like pybossa are Folding@home (Free), Foldit (Free), GridRepublic (Free, Open Source) and Quantum Moves (Free).
Folding@home is a distributed computing project -- people from throughout the world download and run software to band together to make one of the largest supercomputers in the world. Every computer takes the project closer to our goals.
Foldit is an experimental video game about protein folding, developed as a collaboration between the University of Washington's departments of Computer Science and Engineering and Biochemistry (many of the same people who created Rosetta@home).
Quantum Moves, part of the scienceathome.org umbrella concept, was born out of the dilemmas and questions the physics researchers at Aarhus University confronted with when they took the challenge of building a quantum computer in the basement lab of the university.