Did some looking around, and this thread answered some of my questions:
scirra.com/forum/the-business-license_topic47291_page1.html
So if I understand correctly, our options are:
1. Purchase one Personal License per developer. Each can use his/her copy on any computer.
2. Purchase one Business License. Multiple developers can use it as long as it is on only one computer.
3. Purchase one Business License. Only one developer can use it, but it can be used on any computer.
4. Purchase one Business License per developer. Each can use his/her copy on any computer.
But option 1 is only valid if we don't count as a commercial organization. Still wondering about that.