A company's withholding of information about software and copyright can make customers dependent on that company, but this can result in dissatisfied customers if the software does not perform well, and invite unpaid competition which is very difficult for a company to combat.
When customers wish to improve purchased software, they must depend upon the source company to make the programme changes, which it does by hiring programmers to fix the programmes. This is a very inefficient method of change, compared to allowing all users who wish to fix the programme to do so together via a network, such as the Internet.
Using the network, changes to a programme can be made just once by computer programmers among the users, often free of charge, and then tested immediately on thousands of interested users with many different applications, usually at no cost.
On the other hand, if a company make changes to a programme, it must not only fix the programme, but also check that the new version works properly in tandem with other programmes that have been written by its partner companies. Further, the changed programmes are tested formally on a relatively small group of users, so that the likelihood of identifying all new undesirable programme features is lower.
A large software company can try to kill its rivals by starving them of revenue, but this doesn't work against a rival that has no source of revenue.