You can use this on an O2 generator, absolutely, as long as the machine doesn't use more than 650 watts. I have an AirSep O2 generator, it's rated at 4 amps, which, multiply by 120 volts. equals 480 watts, which is well within the capacity of this particular battery backup.
You can use it on just about anything. Besides my PC, I also plug my TV cable box and modem into it because it takes about 5 mins for the cable box to reboot if the power winks out for even a second.