If you played the Dreamcast back in the day, you might remember a piece of software called Bleemcast. This was a Dreamcast version of the PlayStation emulator Bleem, which made it possible to play PlayStation games on Sega's console.
Now, the person who created Bleem, Randy Linden, has been interviewed by Zohar, and the conversation naturally turned to this very emulator, with Bleemcast also coming up. As one might expect, Sony wasn't exactly thrilled that people were emulating their consoles, but the rebels at Sega were apparently all the happier and actually assisted in the creation of this product. Linden explains (transcribed by Time Extension):
"I took a look at the specs for the Dreamcast and thought, 'Yeah, it could be done. Absolutely. Let's get in contact with Sega.' So, we got in contact with Sega, and Sega was thrilled at the idea, and they sent us all the technical specs for the Dreamcast. They loaned us a Dreamcast hardware development system, including a GD-ROM writer and all the necessary software to do the development."
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On the other hand, Sega was a bit more sensible when it came to legal matters and didn't want to make the emulator official or actively participate in its development. That way, they could avoid being sued by Sony, even though they were indirectly involved:
"They did not want the title to be licensed officially by Sega. Because they didn't want to get into a big legal battle with Sony. They would happily license the GD-ROM format and allow us to use their libraries, their code, their whatever, if we got permission from Sony, right? Which was not going to happen. So that meant that everything written for Bleemcast was written from the ground up.
"There are no Sega libraries that are used. There's no Sega code that is used. There's no Sony code that's used, either. But Sega would not license the technology that they had developed for talking to the chips to the hardware. So that's why they sent along all the low-level technical specs, and technical documentation for all the hardware on the Sega Dreamcast."
Thanks to this, it was possible to play PlayStation games on the Dreamcast, and not only that, but the games were also significantly improved. In fact, the Dreamcast unofficially did a better job with this than the PlayStation 2 did. Sony subsequently sued Bleem repeatedly, and even though they didn't win any cases (on the contrary, the courts were on Bleem's side), Bleem still had to shut down because they couldn't afford the legal battle against a giant like Sony.