Well, it would definitely be possible to find something sooner, I'm sure. But:
-Most schools are out over the summer, in north america at least, and I assume europe is on a similar timeline
-This gives plenty of time (five months actually) for the people involved with the foundation to get this organized (I might help after my summer timeline gels). I have a lot of contacts in the west coast Canadian universities and would be happy to see if I can't get my network interested in this.
-Gives lots of time to get the word out and give various bureaucracies to decide give it the go-ahead.
-This kind of thing needs momentum, rome wasn't built in a day, etc.

I think the September timeline is pretty much perfect if targeting universities.

Perhaps do a push with a different vector rather than universities? Maybe try to do a big corporate push? See if you can't get Google or Amazon or any of the big cloud computing orgs to donate a (minimal to them) number of cycles on a given day? Good press, would get other smaller orgs involved, I'm sure. Just a thought.