If you believe the "source" then Kaepernick isn't exactly being blackballed by the NFL, which might be why he hasn't said anything himself about not being on an NFL roster, via The Daily Caller:
"Despite the ongoing narrative that Kaepernick’s very public political views are preventing any NFL teams from offering him a roster spot, TheDC’s source claims Kaep himself has turned down at least one contract in the hopes of stirring up a media frenzy that eventually leads to a more lucrative deal for the 27-year-old vet."
It's a smart move and ESPN is falling right into the trap if it's true. It also stands to reason that the more desperate a team gets, the more money he'll be able to make.
(h/t Daily Snark)