Wikipedia
OtherOS was a feature available in early versions of the PlayStation 3 video game console that allowed other operating systems, such as Linux or FreeBSD, to be installed on the system. This feature was made unavailable in newer models and removed from the oldest ones through a firmware update by Sony.
The "Other OS" feature is disabled by firmware version 3.21 but still runs on older consoles that have firmware 3.15 or lower.
A class action lawsuit was filed against Sony on behalf of those who wished to pursue legal remedies (see PlayStation 3 system software) but was dismissed with prejudice in 2011 by a federal judge. The judge stated: "As a legal matter, [..] plaintiffs have failed to allege facts or articulate a theory on which Sony may be held liable.". However this decision was overturned in a 2014 appellate court decision finding that plaintiffs had indeed made clear and sufficiently substantial claims. Ultimately, in 2016, Sony settled with users who installed Linux or purchased a PlayStation 3 based upon the alternative OS functionality.
Any Linux operating system had access to 6 of the 7 Synergistic Processing Elements; Sony implemented a hypervisor restricting access from the RSX. IBM provided an introduction to programming parallel applications on the PlayStation 3.