RDF serialization - issue with dct:license property

[giorgialodi]

In the RDF serialization of the catalog and datasets, the dct:license property of the Distribution class appears twice. One of the occurrences is semantically correct; the other one is semantically wrong.
This seems happening during the harvesting phase, independently of the type of harvesting (CKAN, RDF, Socrata, etc.)

Example:
Source catalogue: Linked Data platform with metadata compliant with the DCAT-AP_IT specs.

http://dati.beniculturali.it/resource/Distribuzione/complessoArchivistico-GGASI-nt a dcatapit:Distribution,
dcat:Distribution ;
dct:description "Distribuzione in formato N triples del dataset complessoArchivistico-GGASI " ;
dct:format http://publications.europa.eu/resource/authority/file-type/OP_DATPRO ;
dct:license https://w3id.org/italia/controlled-vocabulary/licences/C1_Unknown,
"https://creativecommons.org/licenses/by-nc/2.5/it/legalcode/" ;
dct:title "Distribuzione in formato N triples del dataset complessoArchivistico-GGASI" ;
dcat:downloadURL http://dati.san.beniculturali.it/dataset/nt/complessoArchivistico-GGASI.nt .

There are two values for the dct:license. One is a link to an object of the controlled vocabulary, which is correct. The second value is a string including an URI which is not semantically correct.