Interesting how many people can write but not read.
There is no contradiction with 690 people checking in and 800 people's work - I consider myself a contributor, because I test, report back make bug reports and triage bugs reported by other. But I did not check in any code into KDE since 1999....
So you are forgetting the work of translators, UI testers, bug reporters and other contributors, who contribute but do not check in.
Thus spake the master programmer: "When a program is being tested, it is too late to make design changes." -- Geoffrey James, "The Tao of Programming"