I'm not that much of a fanboy, and not American so have very little interest in NFL... but this does raise some interesting legal questions that very few here could answer, and without actually reading the contract it's all speculation anyway, but it certainly looks like there could be a legal fight. I'll be interested to see how it plays out.
Personally, I'd think Bose and the NFL have overstepped what they're allowed to control, based on the league having sponsors, the teams having sponsors and individual players having sponsors. Obviously, it would be irresponsible for a player to sign a deal with Adidas if their team was sponsored by Nike, as it's a little too close. But if it was only the referees sponsored by Nike, I'd think that would be a fair choice as there's quite a bit of separation there.
In this case, both brands are in the audio field, so they're very close, but it's not a team decision. Further, Apple/Beats didn't sign a deal after Bose, but rather it was the other way around. They knew they'd be causing legal conflicts in contracts with a certain percentage of players (presumably quite high)... so I'd say either Bose or more likely the NFL has promised something that they can't give. Then again, that depends what contracts the players and teams have with the league... I haven't seen them, but I can imagine things are very specific so the NFL better be sure what they've sold can actually be enforced
That's the most interesting part of this. Can a league deal force the players to possibly violate individual contracts, sponsorship and endorsements?
Was thinking it might go the other way, with players forced to not use anything, affecting performance, and then they might say as much in interviews. The league might be sponsored by Bose after all, but if they can't get out of their contracts with Apple the league is putting their own players in a very strange place.
But I do realise it's all about making money, the league doesn't care about their players beyond cashflow.