The actual license from a current OmniFocus disk image reads:
The license permits either (a) multiple users to install and use the Software on a single machine; or (b) a single user to install and use the Software on multiple machines. However, a single license does not allow multiple users to ever use Software on multiple machines, regardless of whether such use is concurrent, except in the case of Family Pack licensing.
So, you can run it on multiple machines so that you can sync between them, but no one else is allowed to use it, if you have a single license.