Last I checked this was in line with the NetBSD license:
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
Yes, it is following the letter of the law, but the NetBSD people are also free to complain about it.
OpenBSD does the same: they list a bunch of vendors at [1] but they note on [2]:
> In the 10 years since the inception of the OpenSSH project, these companies have contributed not even a dime of thanks in support of the OpenSSH project (despite numerous requests).
Surely, everyone is welcome to use the code. But (IMO) some sort of contribution back to the community whether in the form of code or funding would help the ecosystem, especially when a large company like Sony is concerned, which can easily afford this.
It doesn't have to be set down in a contract, but if you explicitly chose to give someone permission to do something, it would be petty to turn around and complain when they did exactly what you told them they could do. This isn't some little loophole Sony's exploiting: It's the largest distinguishing feature between BSD and GPL. If the NetBSD people have a problem with this, there is nothing stopping them from switching to GPLv3 or MPL or anything else. But it looks like they don't actually have a problem with it, and the HN title is editorializing.
EDIT: For posterity, when this thread started, the title was something like "Sony uses NetBSD code in PSP, refuses to contribute back".
"NetBSD code in Sony Playstation Portable
Logix pointed me at the license of the Sony Playstation Portable (PSP), which looks like a bunch of NetBSD code was used. Fun." is a lot more positive than the headline used.
It would be polite, and NetBSD, FreeBSD, and OpenBSD all have frameworks for companies to contribute money. Some folks just don't, but the license doesn't require it.
Companies that modify the code would do well to contribute that code back. It really isn't a matter of nicety in that circumstance, but a cost savings measure. Constantly having to patch after each release or, worse, being stuck because the community picked a different solution since the company's solution was not presented makes for increased costs. Losing the testing and expertise of the community should be incentive enough.
I have never believed requiring participation like a copyleft license would actually improves things. They don't want to engage and forced engagement really isn't going to help you. Let them learn the problems of going it alone.
Sometimes the GPL is a win simply because "otherwise upstream won't have our patches" isn't a high enough short-term cost to overcome the bureaucratic inertia required to release them, but "otherwise we can't use their code at all" makes them compare the cost of license clearance to the cost of reimplementing the GPL'd code.