Hi all!
Regarding accomodation: I've found out that there are numerous inexpensive apartments in Berlin that can be rented for very little money. The sites are mostly German (like http://www.ferienwohnungen-berlin.de/ or www.kostenlose-zimmervermittlung-berlin.de/) but they offer single-bedroom-apartments from as low as 21 EUR (typically though in the 40 to 50 EUR range) per night. They all have their own bathroom, kitchen.
There are also 3/4 bedroom apartments with multiple bedrooms that can be used by e.g. up to 8 people.
If some of the attendees prefer to stay at such a place (as opposed to the hostel or a real hotel), please first coordinate who would all want to stay at the same place and then let me know the total number of beds required. I can look and search for a place that is available and not too distant from the venue (if possible).
Regards, Harald