From http://blog.xen.org/index.php/2008/04/28/xen-api-community-project/:

Several community members have contacted me recently about the Xen-API utilities. I looked into this and discovered a great opportunity for community members looking for a project to contribute to. So, I am announcing a new community effort to complete the development of the Xen-API utilities. If you are interested in working on the Xen-API project please email me at stephen.spector@xen.org and I will call a meeting in mid-May with all people interested to get the project underway.