It should be noted that
registration fees are quite reasonable ($250USD full price, with options of discounts for students, developing countries and early bird before June 1).
For those who are looking for a path towards publishing in the Wiley journal
Systems Research and Behavioral Sciences it's worth noting that the ISSS Yearbook is issue 5 (September-October) in the year following an ISSS meeting.
The deadline for abstracts for Category 1 papers is May 15. Full papers are due June 15.
There are also options for "reports and presentations on work-in-progress, preliminary results and directions of future work" that get published in the proceedings.
If anyone has questions, I was editor of the ISSS Yearbook issue in 2013. Just ask!