Qt can be used commercially under the terms of the LGPL at no cost. When used appropriately (i.e. dynamic linking to unmodified Qt, or, offering source for a m

Qt can be used commercially under the terms of the LGPL at no cost. When used appropriately (i.e. dynamic linking to unmodified Qt, or, offering source for a modified dynamically-linked Qt), the commercial company is not forced to open source anything. Qt has an optional alternative license with a cost attached, that gives you (A) a support contract, and (B) additional rights (static linking without invoking GPL virality, private modifications, ...).