The original IBM PC had pretty open hardware and software, both a little unintentional. Hardware-wise they published everything so add-in cards and more could be developed. Sofware-wise they didn't hold Microsoft to an exclusive agreement for PC-DOS so MS-DOS could come out.

Later they tried to close the barn door with very locked down hardware with the microchannel bus and IBM's own operating system OS/2. But it was too late...

I actually think Apple and their customers would be more successful with open hardware. When they went from powerpc to intel with more generally compatible hardware, I think that was great. Now they're reeling it back in, and I wonder if they'll be following the same path as IBM did...