The Reciprocal Public License (RPL) is interesting in that it is the only license both OSI-approved and not FSF-approved. It is a copyleft license similar to GPL but with a "reciprocal" clause:
Regarding deployment, under the RPL your changes, bug fixes, extensions, etc. must be made available to the open source community at large when you Deploy in any form -- either internally or to an outside party. Once you start running the software you have to start sharing the software.
RPL 1.5, preamble
Specifically, clauses 6.0 and 6.1 require that any private modifications must be provided back to the licensor and the public respectively, under the RPL.
Why is this license approved by OSI but not by the FSF? Which specific essential freedoms, if any, does RPL violate? Why doesn't RPL violate any of the Open Source Definitions?