You should be good if you ride it for some decent miles a couple of times a week or hell even once a week. The battery tender is more important when it will set there for say over a week or more, like months.
As far as I know it will not work coming off a DC supply. It will help prolong the battery life if used to keep the battey up to idea condition, but will not make it last forever. Anything over about 2 years on our type of AGM batteries is pushing it anyway. The battery tender will help drag it out longer, where if not used, the battery will fail earlier unless you are lucky enough to have consistent rding through out the year and get some miles on it.
If possible get youself a good extension cord and drag it out to where you can put the BT on the bike for those long non-running time. If you do, get a good extension cord, something like contractors use (like those good ole Orange HD or Yellow ones).