関連ワード:  open source software means free to    open source software is free to use and modify    open source software is free of cost    open source software is always free to use    open source software is always free to use and modify    open source software is always free of cost    open source software is available free of cost true or false    is open source software free to use    photoshop is open source software which means it is free to use    what is free open source software