Here are excerpts from the email I received from Peter Weik:
As you were asking in the latest post for links on what could be done, that exploit what IMS and SIP can offer to deliver innovative services I had to take on that opportunity as one of the lead developers of an open source project ;)
Well, you could spread the word even more via a blogpost that there is a free open source solution out there that has already enabled many IMS testbeds and developers: the Open IMS Core (www.openimscore.org).
The Open IMS Core is an implementation of IMS Call Session Control Functions (CSCFs) and a lightweight Home Subscriber Server (HSS), which together form the core elements of all IMS/NGN architectures as specified today within 3GPP, 3GPP2, ETSI TISPAN and the PacketCable initiative. The four components are all based upon open source software(e.g. the SIP Express Router (SER) or MySQL) and are available under the GPLv2. (You may know the project since it is also in the The March 2007 special issue of the IEEE Vehicular Technology Magazine on IMS, just three articles further onwards.) The whole idea behind the project is to enable IMS developments and to help an industry to adopt IMS concepts - all of it without huge investments necessary.
Besides sparking the development of two also freely available IMS clients (the IMS Communicator and the UCT IMS Client), it has also enabled some industry players, universities and R&D departments (see www.openimscore.org/quotes) and is used in current IMS interop events (e.g. at University of New Hampshire, http://www.iol.unh.edu/services/testing/voip/equipment.php#IMS).
But of course we are also looking at own application prototype developments as part of our recently started Open SOA Telco Playgroundxggveqt (www.opensoaplayground.org). What is possible with IMS was shown at our last IMS workshop in November 2007 with the IMS Community Mashup with Facebook (http://youtube.com/watch?v=b1OwDD6cyBY).