Broncos and Elway wanted Kapernick last year.  Kapernick shunned the Broncos and refused to accept a pay cut.  That is the main reason Broncos have no interest in Kapernick this year.  It is similar to the Osweiller situation.  If Brock was cut, the Broncos will have no interest him now because the relationship is broken (when Brock chose Houston).

As far as Kap being shunned by NFL teams, the rule is simple in sports.  If you are an elite (or) even a good player, then you will get 2nd and 3rd chances.  Greg Hardy and Joe Mixon got 2nd chances.  But if you are an average (or) sub-par player, then you better not get in trouble with the law (domestic abuse, guns, assault etc.) or garner negative publicity for the team with your political/religious/cultural stand.  Kapernick is an average player at this stage.  

Teams are weighing the pros and cons of signing Kap.  Right now the cons outweigh the pros.  Hence he is unsigned.