Probably means they wont sue you or bill you if you use it in your own processor designs. The article mentioned releasing a softcore for FPGA; that at least means you can run the instruction set on something. There are even enthusiasts that might be interested in using an FPGA to build a whole computer; for example the Amiga community have a PowerPC based operating system. Instruction sets must also be an acquired taste; Power seems complex to me; but a lot of people clearly like it.