mharr wrote:Are there deep copyright reasons that companies never use one of the amazing open source emulators that aleady exist, or is it mostly just Not Invented Here syndrome?
In Nintendo's case, I think it's specifically because they refuse to legitimize anyone else's emulation project but their own; their stance is that all emulation is piracy.
Speaking more generally, some of the reasons are technical, like Newbie said, and some are from licensing, like Mongrel and Brent said.
Some "open-source" emulators actually aren't; the emulator Capcom pirated* was published under a license that forbid commercial sale. I believe SNES9x still has a similar clause in its license.
Thing is, though, I wouldn't count those as "open source emulators" because any license with a noncommercial clause is, by definition
, not open source. "Open source" doesn't just mean source code is published and available; it's a term of art with a specific set of criteria, and any license that forbids commercial sale does not meet those criteria. (Specifically, criterion 6, No Discrimination Against Fields of Endeavor.)
But even among actually-open-source emulators, some companies won't touch the GPL, because it means they'd have to license their modified software under the same license. (This is why consoles tend to run FreeBSD, not Linux. Except for MS consoles, which of course run Windows.)
There have been some cases where companies have used open-source emulators, though. The PlayStation Mini used PCSX ReARMed.
Can't find a source but I remember reading that at one point Sega bought an open-source emulator out and used it in some official product or other. I think that would still count as an example of a company using an open-source emulator, even if their derivative version was proprietary.
* Capcom actually got a waiver on the noncommercial clause from the project team, but not from every developer who owned a share of the copyright in the codebase. It's a bit more complicated than "pirated", but as I'm confident Capcom wouldn't say "hang on, it's a little more complicated than that" if they caught someone infringing their
copyrights, I'm more than comfortable just stating that Capcom is a filthy, filthy pirate.