Alternative see the lessphp Project: https://github.com/leafo/lessphp
Works fine and hase an team of contributor. But has not an out of the box function for WordPress; but uts only PHP and the WP has the right Hooks. Do you will only use in themes, then its also fine, that you include this and it works with your requirements and no dependencies to an plugin.
For an easy use in WP, see this project https://github.com/sanchothefat/wp-less
its an wrapper and use lessphp; but an new dependencies. But its better as an plugin, if the customer change the plugin with updates and other doings, and easy to use.