I'm not sure it's possible to give a precise economic definition of "indie". The term originated in the music world and referred to rock bands that refused to sign with major record labels. It was adopted by the movie business to refer to film-makers that did not work with the big production companies. IMO, "indie" has as much a cultural connotation as it does economic content, e.g.: small-scale start-ups, craftsmen working on "handmade" skis in converted garages, sawdust on the floor, etc. Like Stonyfield yogurt compared to Dannon; Turner bikes vs. Trek.
So, some suggested indicators for determining whether ski manufacturer is an "indie":
(b) its website includes pictures of its factory and/or workers (see: http://on3pskis.com/ , http://www.icelanticboards.com/#/skis/factory-tour);
(c) the company does not also make tennis rackets, defense articles, etc.