While I’m not yet we’ll-versed in how the new rights management will work, the main limits I would suggest would be:
- Max 3 spaces
- Max number of editors and admins
- Maybe a max number of databases (e.g. 20)
Of course these numbers can be abused, which is why a “fair-use” clause should be there too.
For a sports or special-interest club I see that it would allow to:
- Track member signup
- Track membership payments
- Track and announce events
- Plan event attendance
- Track equipment
- Build an internal knowledge base
I think 3 spaces make conceptually sense as It allows for one space for decision makers, one for all members and one extra. That should generally suffice.
And yes, there is a discount pricing for non-profits (many thanks), but the kind of setup I’m thinking of (e.g. 7th tier football club, local hashers, Guggenmusik carnival music band, student magazine, community centre, parents’ group, small scale art festival or volunteer fire brigade) is not the typical “non-profit NGO” like AI, Greenpeace or Oxfam. 
In the end, I see it more likely that I can expose and convert people into Fibery fans through soft-conversion (getting them to use it for one of my extra-currciculars) than by hard-conversion (a mandated switch at work from an existing system to Fibery).
With the hard-convert the focus will always be on what’s missing, while with the soft convert the focus is on how much better it is than what’s there currently. And the good news is that with the recent polish a lot of stuff’s good enough to allow for that.