I.B.M. plans to announce today that it is making 500 of its software patents freely available to anyone working on open-source projects, like the popular Linux operating system, on which programmers collaborate and share code.

The new model for I.B.M., analysts say, represents a shift away from the traditional corporate approach to protecting ownership of ideas through patents, copyrights, trademark and trade-secret laws. The conventional practice is to amass as many patents as possible and then charge anyone who wants access to them. I.B.M. has long been the champion of that formula. The company, analysts estimate, collected $1 billion or more last year from licensing its inventions.