3rd party dependencies are a good point. Though we are talking about a 35 year old OS whose last incremental update was 16 years ago and last major release about 25 years ago. We are also talking about a non-profit inheriting the codebase. Seems like the lawyers could probably figure something out given these constraints.

Irix did a lot of things in-house and the value of the OS is not generally in commonly available components. I suspect that any 16-25 year-old 3rd-party components that are of any value have modern equivalents which are open-source and probably better in most ways. I would think there is a way of putting the burden of sorting through these issues onto the non-profit receiving the rights much as the burden was passed to HP through an acquisition in the first place.