1. Avian-paramyxovirus cDNA at least comprising a nucleic acid sequence corresponding to the 5'-terminal end of the genome of avian-paramyxovirus allowing generating an infectious copy of avian-paramyxovirus. 2. A full-length avian-paramyxovirus cDNA at least comprising a nucleic acid sequence corresponding to the 5'-terminal end of the genome of avian-paramyxovirus allowing generating an infectious copy of avian-paramyxovirus. 3. A cDNA at least comprising a nucleic acid sequence corresponding to the 5'-terminal end of the genome of avianparamyxovirus allowing generating an replicating avian paramyxovirus minigenome. 4. A cDNA according to any one claims 1-3 at least partly derived from Newcastle Disease Virus. 5. A cDNA according to claim 4 wherein said Newcastle Disease Virus is a lentogenic virus, preferably derived from a vaccine strain. 6. A cDNA according to claim 5 wherein said vaccine strain is a LaSota strain ATCC VR-699. 7. A cDNA according to any one of claims 1 to 6 additionally provided with a modification in a nucleic acid of said cDNA. 8. A cDNA according to claim 7 wherein said modification comprises a nucleic acid encoding a modified protease cleavage site. 9. A cDNA according to claim 8 wherein said cleavage site is a protease cleavage site of the fusion (F) protein. 10. A cDNA according to claim 7 wherein said modification comprises a nucleic acid encoding a hybrid viral protein. 11. A cDNA according to claim 10 wherein said protein is a hemaglutinin-neuraminidase (HN) protein. 12. A cDNA according to claim 7 wherein said modification comprises a deletion in a nucleic acid encoding a viral protein. 13. A cDNA according to claim 12 wherein said viral protein is a matrix (M) protein. 14. A cDNA according to any one of claims 1 to 13 additionally provided with a nucleic acid encoding an heterologous antigen. 15. A cDNA according to claim 14 wherein said antigen is derived from a poultry pathogen. 16. A cDNA according to claim 14 or 15 additionally provided with a nucleic acid encoding an immune-stimulatory protein or part thereof. 17. An RNA obtained from a cDNA according to anyone of claims 1 to 16. 18. A method for generating protein using an replicating avian paramyxovirus minigenome, comprising transfecting at least one cell with cDNA according to claim 3. 19. A method for generating infectious copy avian paramyxovirus comprising transfecting at least one cell with cDNA according to any one of claims 1, 2 and 4 to 16. 20. A method according to claim 19 wherein said cell is at least capable of expressing viral nucleocapsid (NP), phospo (P) or large polymerase (L) protein. 21. A method according to claim 19 or 20 further comprising allowing cleavage of the fusion protein of said virus. 22. A method according to anyone of claims 18 to 21 further comprising incubating said cell in growth medium comprising proteolytic activity. 23. A method according to claim 22 wherein said growth medium comprises allantoic fluid comprising said proteolytic activity. 24. A method according to anyone of claims 18 to 23 wherein said cell is derived from a chicken cell. 25. An infectious copy avian-paramyxovirus obtainable by a method according to any one of claims 19 to 23. 26. A vaccine against infectious diseases and/or cancerous tissue, comprising the infectious copy avian-paramyxovirus according to claim 25. 27. A vaccine according to claim 26 wherein said vaccine is a live vaccine. 28. A vaccine according to claim 26 or 27 wherein said infectious copy avian-paramyxovirus is at least partly derived from a Newcastle Disease Virus (NDV). 29. An animal vaccinated with a vaccine according to any one of claims 26-28. 30. A method for distinguishing unvaccinated animals or animals vaccinated with a NDV vaccine according to claim 29 from animals infected with wild-type NDV or vaccinated with an unmodified mesogenic or lentogenic NDV strain comprising taking a least one sample from said animal and determining in said sample the presence of antibodies directed against an immunodominant epitope or marker expressed by said wild-type or unmodified NDV but not by said vaccine. 31. A method according to claim 30 wherein said antibodies are directed against the HN or F protein of NDV. 32. A method according to claim 30 or 31 wherein said animal is selected from the group composed of poultry, preferably of chickens. 33. A diagnostic kit for use in a method according to any one of claims 30 to 32, said kit comprises a specific immunodominant epitope expressed by wild-type NDV and said epitope is not present in said NDV-vaccine according to any one of claims 26-28, said kit further comprises means for determining the presence of antibody associated with said epitope.