Seems a reasonable explanation, a "free" party is an oxymoron. In Glasgow, we just call it a "Party". Seems to work for us.
Since raving went mainstream in the 90's organisers started charging. Free party is more of a push back against the commercialisation of drug enduced dance music .
Warm Scrumpy Jack is ****ing rank That stuff gives you explosive ****s too. Try to do one whilst arriving at the station and everyone is queueing by the bogs