Any manufacturers software is specific to the system is it controlling no matter who supplies the equipment. It is the supply of that equipment and the programming software that becomes open and closed protocol.
The manufacturer will only supply the software that controls equipment to their own company operatives which only allows their engineers to carry out any software modifications to the system it is controlling. In doing this they can keep the aftermarket service prices extremely high, this means that additional work or repair work is very difficult to budget for.
The manufacturer will supply the software and a license for a particular site only this means that the customer can offer the work required to a contractor who is then trained by the particular manufacturer and that contractor then having a licence to operate that particular software. There is normally an additional charge for the licence and training for whomever the customer chooses.
The manufacturer will have various supply outlets or contractors who they offer training, software and supply of all their equipment to. This means that your chosen contractor can offer you a full package from supply of the equipment to the end commissioning work. Also this means if you chose another contractor the manufacturer will give you a list of their authorised suppliers. This allows you to look for the most competitive prices in the market.