Open Source License Model - What is it ?

Could you tell me what an Open Source License model is (With respect to GNU GPL or LGPL) and what would be the advantages and disadvantages of using it ?

We are looking to develop an application that will run on a PC and MAC and can be distributed freely to an unlimited number of users at no cost. Would an Open-Source license allow this ?

Is GNU GPL or LGPL fully supported and can a developer ask questions to resolve bugs if necessary ? Thanks.


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