I'm not greatly familiar with either of these (I follow the 40 foot pole rule in this regard), but it does appear that they both need them. It's a bit shocking to me, but if you turn off JS and go to the LESS website, no styles load at all. :eek2:
If server-side is possible for both of these, what is easiest way of setting these up server side and so that it's the lightest load on the server too?
Probably best to read the respective websites for info on that. LESS can be set up with server-side JS using Node.js. (Sounds a hell of a lot easier just to use real CSS, if you ask me. )