NEW YORK ( TheStreet) -- I have covered open source software since 2005, and tracked how companies manipulate the rules of open source to suit themselves. In 2006, I wrote at ZDNet about what I called the open source incline, the idea being that the more even-handed the license, the more likely it was people would contribute code and other help to a project. The news peg here was a company called Appcelerator, which was then gaining significant developer support by licensing its mobile app code under the General Public License, or GPL. This requires that companies offer back their contributions to the code, while the Apache or Eclipse licenses let companies make enhancements proprietary. In 2008, I wrote at ZDNet about what I called the open source development incline, the idea being that a project's development model can affect how code contributors react to it. The news peg here was the battle over OpenStack, the open source cloud infrastructure. Rackspace ( RAX) had been the original corporate sponsor, but it was then feeling pressure -- to which it later succumbed -- to place the code into a separate foundation that other companies could join. In 2010, I completed my ZDNet trilogy with this ZDNet article on what I called the open source copyright incline. Here, the idea was that where copyright is assigned also matters to contributors. I wrote this after Oracle ( ORCL) tried to use copyright to seize control of open source projects it bought with Sun Microsystems. How open is any code, even GPL code, if a company can assert proprietary rights through copyright to what others wrote for it? Fortunately, courts have not seen fit to make open source a dead letter over this claim. Today it's time for a fourth dimension, which I'll call the access incline. Even if a project is open source, even if it's established, it can collapse if corporate contributors simply decide not to support it, or to restrict support of it by outside developers. The news peg here is Google's ( GOOG) decision to close out Google Reader, and, as CNET notes, close out all support for the Real Simple Syndication, or RSS, standard that Google Reader uses. The aim, as Felix Salmon writes at Reuters, seems clear: to keep users from regularly accessing data outside the Google walled garden. Controlling access to code is as important as the rules under which code is produced. This is true whether or not the code is open source. Facebook ( FB), for instance, wants to control who can access its Social Graph feature, as TechCrunch writes. Wise readers may notice that the company they're all emulating here is Apple ( AAPL), which first charged 30% of publishers' gross to sell on iTunes.