Liberté, égalité, fraternité
This famous phrase is the hallmark of the 1848 Revolution, the one that was stirring in 1844 when Dumas penned The Three Musketeers. The weight of the phrase is present in the novel and the play.
In the play, the Musketeers want liberty for their country and for the government--liberty from the oppressive regime of Cardinal Richelieu which takes power out of the hands of the French monarchy. There is also an incurrent of personal liberty, that the characters in the play should be free to love who they want to love.
Perhaps represented the most by the character of Sabine in Ludwig's Three Musketeers. Sabine wants to be treated as an equal, as she possesses the same skills as her brother, limited only by her gender and the time period. Sabine shows the audience that she is an equal to the men in the play as she participates in the major plots and kills Milady--a representation of the older model of woman. Sabine pursues Aramis in a way that is more stereotypically masculine for the time. Sabine, in many ways, is Marianne in the play.
There's nothing more important to our heroes than their friendship. The musketeers treat each other as brothers and that's what helps them win the day. Milady, Rochefort, and the Cardinal do not have the same love for each other so they are incapable of working together as well as our four (five) heroes do.