There is no strict definition for open source science, otherwise known as open science. However, generally open science is taken to follow four main doctrines: “open source, open data, open access, open notebook.” More clearly, this spells out transparency in scientific methodology, public availability of scientific data and communication, and using the Internet to spread this all around.
Open science has a number of advantages. Most notably, it will help scientists collaborate with each other: with the free flow of knowledge also comes staggeringly faster development speeds that can take science to places where today we may not have even dreamed of. It also allows scientists to reanalyze the raw data of the experiments of others, which can result in vastly different conclusions that can spark discussion and development.
“Innovation lies at the intersection of disciplines” is a common quote amongst scientists: while the a problem may lay within one field of expertise, the solution may lie in another one entirely. Numerous examples, from field testing DNA kits to X Prize winners, attest to this fact. After all, it was open science-style agreements that allowed for the Human Genome Project to take place.
There are a number of models in which such mass collaborative science can function, all with their advantages and disadvantages. All of them deemphasize publication as the sole purpose of research, as is often the case for scientists today.
There's been a certain loss of faith in the scientific community of late, which open science also hopes to address. By letting the general public in on what scientists are doing, it's hoped that everyone will become interested in science again and what it can accomplish, and not just doubt its veracity.