There is a filter to filter out licenced content, which I cannot describe in great detail, as I use an older version of Limewire which does not have it. I cannot use the current version on my ageing Mac
It is optional to use it, but it is a feature that Limewire has developed, and is in the spirit of the Limewire insistence that Limewire not be used for downloading or sharing copyright material. I hope that my answer makes sense