Thanks for the response, but i see the problem quite differently.
In fact it isn't exactly that my UPS isn't supported, the problem is that Open-e just not support UPS's from MGE in slave mode or in master mode !
It is a pity, cause i've bought a 2200VA UPS to support several servers attached, BUT i can only connect the Open-e server cause Open-e cannot work as a master or as a slave because you just haven't implemented all the features of NUT (http://www.networkupstools.org/) in the NAS XSR edition:
So my feeling is that if you choose to buy an MGE UPS, you will only be able to connect THE "Open-e" server to the UPS.
What is strange, is that if i choose an UPS model from APC, there are the options to choose slave and master mode, so why don't you implemented it for MGE as well ?