Less CSS is similar to SASS, with a slightly different syntax (which is compatible with css).
It is also made with Ruby. They explain their difference with SASS
So why make an alternative to Sass? It’s simple: syntax. One of the key features of Sass is its indentation-based syntax, which gives you curly-brace and semi-column free code. But the cost of this is having to learn a new syntax and having to rebuild your current stylesheets.
LESS embraces CSS, and any additional functionality it comes with, is integrated in such a way as to make it as seamless as possible. Thus, you can gradually move your CSS to LESS, or if you’re only interesting in using variables, or operations, you aren’t forced to learning a whole new language.
License is Apache Licence 2.0
Pros and cons are similar to SASS, but there is no Compass equivalent.
But the fact that the syntax is css means that you can intregrate css frameworks (like YUI, 960.gs) without having to “adapt” them. And the IDE support might be a bit better since their syntax is closer to CSS.
Less has RoR integration too (and it’s called more, obviously).
