The calendar pal is laying around here somewhere. I'll dig it out this coming week and put in to the next minor upate for IIP. I have IIP working with the upcoming release of .threads and will post the updated IIP when .threads 6.2 is pubicly available.
As far a server load with the calendar addon I don't think smaller sites will have much of an issue with it. I was considering the "what if" when a site has 10 or 20 users browsing the calendar and possibly creating 300 - 800 queries in that area alone.
I think Dave_L will have this problem resolved though.