As a corporation you open source at least pieces needed for interoperability, that is a valid reason. Otherwise you can get into the pains of SMB/Samba or drive

As a corporation you open source at least pieces needed for interoperability, that is a valid reason. Otherwise you can get into the pains of SMB/Samba or drivers for paid databases for more programming languages one is able to support. For example Microsoft is working on the PHP driver for SQL server, this helps them by opening the door to PHP developers to use MS SQL and eventually pay for Standard or Enterprise editions instead of using the free Express one. It is kind of a freemium game.