jammag writes: "Bruce Perens, who wrote the original licensing rules for Open Source software in 1997, notes that there a sprawling 73 open source licenses that now exist. But he identifies an essential 4 — well, actually just 2 — that developers, companies, and individuals need. In essence, he cuts through the morass and shows developers, in particular, how to protect their work. (And yes, he favors GPL3 over GPL2). For his own coding work, he's fond of the "sharing with rules" license, which stays true to the Open Source ethos of shared code yet also enables him to get paid by companies who use it in their commercial products. Consider this the essential guide."