There are perhaps 2500-3000 unique open source licenses, ranging from the half dozen most of you will know well to very obscure licenses which have come about because (for example) a research grant from a foundation with certain guiding principals indirectly paid for some of the development of some software as part of a larger research initiative. There's even a license that precludes use of the software in any military equipment other than that which is strictly of a defensive nature, due to the constitution of the country sponsoring (a small part of) the project.