Your right, of course it's not worship (ibadah), but rather it's more like devotion. Singing nasheeds and stuff in groups is to build love for Allah and the Prophet (s) and to motivate each other etc. The sahaba recited poems and songs, (like when the Prophet(s) arrived to madinah) and it didn't seem to be a problem. As far as I understand, it would be bidah to insist that doing this is somehow an obligatory form of worship, but people do it with the understanding that it isn't.
Dhikr is worship, it is fard to make dhikr (in general) and love of Allah and his Messenger is FARD!!!!! And the means to things take the rulings of the things. (Ex: it isn't fard to take a boat ride intrinsically, nor to fly, but if you live in America and can afford hajj, it becomes FARD for you to find a way, and a boat or plane or whatever takes that fard ruling...so specifically, no a person doesn't have to recite this nasheed, but the results (dhirk and love of Allah and His Rasul (Salla_Llahu 'alayki wa salam)) is fard.
