Do you remember Hudson CI? If you did some CI two years ago then you know Hudson and you also know that after the acquisition of Sun by Oracle there was hassle in the community. End of story was that the lead developer Khosuke and some of his fellows spun of the Jenkins project. That’s the short version. For the longer one ask the search engine of your choice.
But one import issue for newbies to CI is the question: Which project should we use? If you see the numbers the answer is quite clear:
|User upgrades since March 2011||85%||15%|
|User upgrades since March 2011||2300||300|
|Average # of commits in plugins/week||280||16|
|User + Dev mailing list traffic/week||1295||299|
|Dev list subscribers||1150||508|
|Dev list growth since March 2011||+41%||-7%|
|User list subscribers||2084||800|
|User list growth since March 2011||+62%||-8%|
The numbers are from this PDF.