Interesting one this, there are a huge number of amateur performers willing to play anywhere for free, which is of course why we see so many open mike nights these days, and they of course have the freedom to make that choice, as has been pointed out, does anyone who works as a volunteer, goes out with a morris side etc,etc.

I know nothing about Cinderford, so can only go on what is on their facebook page, and it appears to be an event with free admission, so presumably the organisers have all the infrastructure costs to bear, and are doing it for the love of the music.

On the basis that the event is free, so I would assume that no-one is making money out of it, then it becomes purely a matter of personal choice to perform at it.

If it was an event where there was an admission charge, one would then expect the organisers to have a budget to pay performers, so it becomes again a different situation and I would not expect myself to perform for nothing at an event of that nature. Again, if the event is to raise funds for a specific charity, it is a matter of personal choice for the artist if they wish to donate their services for that cause. I organise a weekend raising money for Oxfam, and the artists come a volunteers, and only those who are not local will get a few bob from the proceeds to cover expenses.