(Disclaimer: speaking only for the legal jurisdictions with which I have familiarity, and acknowledging that any random jurisdiction can codify arbitrarily insane restrictions that I haven't accounted for.) "tying" doesn't apply here for numerous reasons. Most importantly, the GPL licenses of the third-party software in question *already* apply the same conditions regardless of the involvement of Busybox, and the companies already choose to use that software independently of their choice of Busybox, which means they need to satisfy the license on that software. That alone makes this in no way "tying". Apart from that: 1) this only applies to companies violating copyright on both Busybox and other GPLed programs, which puts those companies in the position of violating the law to begin with; 2) Busybox has no obligation to grant a new license at all, and could just say "stop using Busybox in all your products and take them off the market"; 3) this represents a legal settlement agreed to by the company violating the GPL, in lieu of risking the remedies applied by a court, which would not typically include the release of source code; and 4) this doesn't represent a "sale" of either Busybox or other GPLed programs, but a grant of permissions the company in question would not otherwise have, namely to redistribute (and potentially modify) the programs in question.