> I wonder how many companies really had to change the source code of git, subversion, mercurial etc.
Even that overstates the matter. Companies could modify the code all they want as long as they don't distribute that code. That would impact Github competitors - maybe 10 or 20 companies in the entire US.
Facebook uses derivatives of PHP and mySQL today, because those are the technology choices Zuckerberg made in 2004. You hope you should be so lucky!
Also, "distribute that code" can be interpreted very broadly. A contractor may access your internal HR system, and now you have to share it with them. A factory line worker may be entitled to the source controlling the robot fixture. A airline passenger may use the in-flight entertainment unit, and be entitled to its source. Etc.
If the HR, the robot and the entertainment systems are AGPL licensed chances are that their source is already on github.
Spot on for PHP and MySQL. PHP has its own license (kind of BSD?) and MySQL is GPL2 or commercial. I bet Facebook could buy the rights of any AGPL product, unless the owner is really firm about principles.
Even that overstates the matter. Companies could modify the code all they want as long as they don't distribute that code. That would impact Github competitors - maybe 10 or 20 companies in the entire US.