Restrictions in license

[Joerg Friedrich]

Hi,
 
let's assume I would take an OSI approved license like the Apache License
2.0 for some server software (e.g. a web server), and would add a user
limitation to this license in a way that the license for the server software
and all derived work carries this user limitation. Other than that there
would not be any restrictions.
 
Would you still consider this an Open Source license in the spirit of the
OSD? If not, which part of the definition would this go against?
 
Thanks for your thoughts on this.
 
Joerg