The effective license of the modules as a whole is the GNU General Public License Version 2 (GNU GPL-2).
Single files, however, are licensed either under GNU General Public License Version 2 (GNU GPL-2) or under "GNU GPLv2 or any later version" (GNU GPL-2+).
GPL-2: See file COPYING
The following list was created using the 'licensecheck' tool with the following command:
licensecheck -r --deb-fmt <directory>
src/CMakeLists.txt: GPL-2+ src/attack.c: GPL-2 src/attack.h: GPL-2 src/attack_tests.c: GPL-2+ src/debug_utils.c: GPL-2+ src/debug_utils.h: GPL-2+ src/hosts.c: GPL-2 src/hosts.h: GPL-2 src/main.c: GPL-2+ src/nasl_plugins.c: GPL-2 src/openvas.c: GPL-2 src/openvas.h: GPL-2+ src/pluginlaunch.c: GPL-2 src/pluginlaunch.h: GPL-2 src/pluginload.c: GPL-2 src/pluginload.h: GPL-2 src/pluginscheduler.c: GPL-2 src/pluginscheduler.h: GPL-2 src/plugs_req.c: GPL-2 src/plugs_req.h: GPL-2 src/processes.c: GPL-2 src/processes.h: GPL-2 src/sighand.c: GPL-2 src/sighand.h: GPL-2 src/utils.c: GPL-2 src/utils.h: GPL-2
nasl/CMakeLists.txt: GPL-2+ nasl/arc4.c: GPL-2+ nasl/byteorder.h: GPL-2+ nasl/capture_packet.c: GPL-2 nasl/capture_packet.h: GPL-2 nasl/charcnv.c: GPL-2+ nasl/charset.h: GPL-2+ nasl/exec.c: GPL-2 nasl/exec.h: GPL-2 nasl/genrand.c: GPL-2+ nasl/hmacmd5.c: GPL-2+ nasl/hmacmd5.h: GPL-2+ nasl/iconv.c: GPL-2+ nasl/iconv.h: GPL-2+ nasl/lint.c: GPL-2 nasl/lint.h: GPL-2 nasl/md4.c: GPL-2+ nasl/md4.h: GPL-2+ nasl/md5.c: public-domain nasl/md5.h: public-domain nasl/nasl-lint.c: GPL-2+ nasl/nasl.c: GPL-2 nasl/nasl.h: GPL-2 nasl/nasl_builtin_find_service.c: GPL-2 nasl/nasl_builtin_openvas_tcp_scanner.c: GPL-2 nasl/nasl_builtin_plugins.h: GPL-2+ nasl/nasl_builtin_synscan.c: GPL-2 nasl/nasl_cert.c: GPL-2+ nasl/nasl_cert.h: GPL-2+ nasl/nasl_cmd_exec.c: GPL-2 nasl/nasl_cmd_exec.h: GPL-2 nasl/nasl_crypt_helper.c: GPL-2 nasl/nasl_crypto_helper.h: GPL-2 nasl/nasl_crypto.c: GPL-2 nasl/nasl_crypto.h: GPL-2 nasl/nasl_crypto2.c: GPL-2 nasl/nasl_crypto2.h: GPL-2 nasl/nasl_debug.c: GPL-2 nasl/nasl_debug.h: GPL-2 nasl/nasl_frame_forgery.c: GPL-2+ nasl/nasl_frame_forgery.h: GPL-2+ nasl/nasl_func.c: GPL-2 nasl/nasl_func.h: GPL-2 nasl/nasl_global_ctxt.h: GPL-2 nasl/nasl_grammar.y: GPL-2 nasl/nasl_host.c: GPL-2 nasl/nasl_host.h: GPL-2 nasl/nasl_http.c: GPL-2 nasl/nasl_http.h: GPL-2 nasl/nasl_init.c: GPL-2 nasl/nasl_init.h: GPL-2 nasl/nasl_isotime.c: GPL-2+ nasl/nasl_isotime.h: GPL-2+ nasl/nasl_lex_ctxt.c: GPL-2 nasl/nasl_lex_ctxt.h: GPL-2 nasl/nasl_misc_funcs.c: GPL-2 nasl/nasl_misc_funcs.h: GPL-2 nasl/nasl_packet_forgery.c: GPL-2 nasl/nasl_packet_forgery.h: GPL-2 nasl/nasl_packet_forgery_v6.c: GPL-2 nasl/nasl_packet_forgery_v6.h: GPL-2 nasl/nasl_raw.h: GPL-2 nasl/nasl_scanner_glue.c: GPL-2 nasl/nasl_scanner_glue.h: GPL-2 nasl/nasl_signature.c: GPL-2+ nasl/nasl_signature.h: GPL-2+ nasl/nasl_smb.c: GPL-2+ nasl/nasl_smb.h: GPL-2+ nasl/nasl_snmp.c: GPL-2+ nasl/nasl_snmp.h: GPL-2+ nasl/nasl_socket.c: GPL-2 nasl/nasl_socket.h: GPL-2 nasl/nasl_ssh.c: GPL-2+ nasl/nasl_ssh.h: GPL-2+ nasl/nasl_text_utils.c: GPL-2 nasl/nasl_text_utils.h: GPL-2 nasl/nasl_tree.c: GPL-2 nasl/nasl_tree.h: GPL-2 nasl/nasl_var.c: GPL-2 nasl/nasl_var.h: GPL-2 nasl/nasl_wmi.c: GPL-2+ nasl/nasl_wmi.h: GPL-2+ nasl/ntlmssp.c: GPL-2+ nasl/ntlmssp.h: GPL-2+ nasl/openvas_smb_interface.h: GPL-2+ nasl/openvas_wmi_interface.h: GPL-2+ nasl/proto.h: GPL-2+ nasl/smb.h: GPL-2+ nasl/smb_crypt.c: GPL-2+ nasl/smb_crypt.h: GPL-2+ nasl/smb_crypt2.c: GPL-2+ nasl/smb_interface_stub.c: GPL-2+ nasl/smb_signing.c: GPL-2+ nasl/smb_signing.h: GPL-2+ nasl/time.c: GPL-2+ nasl/wmi_interface_stub.c: GPL-2+
nasl/tests/Makefile: GPL-2+ nasl/tests/signed.nasl: GPL-2+ nasl/tests/test_blowfish.nasl: GPL-2+ nasl/tests/test_bn.nasl: GPL-2+ nasl/tests/test_crypt_data_aes.nasl: GPL-2+ nasl/tests/test_dh.nasl: GPL-2+ nasl/tests/test_dsa.nasl: GPL-2+ nasl/tests/test_hexstr.nasl: GPL-2+ nasl/tests/test_isotime.nasl: GPL-2+ nasl/tests/test_md.nasl: GPL-2+ nasl/tests/test_privkey.nasl: GPL-2+ nasl/tests/test_rsa.nasl: GPL-2+ nasl/tests/test_socket.nasl: GPL-2+ nasl/tests/testsuiteinit.nasl: GPL-2+ nasl/tests/testsuitesummary.nasl: GPL-2+
misc/CMakeLists.txt: GPL-2+ misc/bpf_share.c: GPL-2 misc/bpf_share.h: GPL-2+ misc/ftp_funcs.c: GPL-2+ misc/ftp_funcs.h: GPL-2+ misc/ipc.c: GPL-2+ misc/ipc.h: GPL-2+ misc/ipc_openvas.c: GPL-2+ misc/ipc_openvas.h: GPL-2+ misc/ipc_pipe.c: GPL-2+ misc/ipc_pipe.h: GPL-2+ misc/network.c: GPL-2+ misc/network.h: GPL-2+ misc/nvt_categories.h: GPL-2+ misc/pcap.c: GPL-2+ misc/pcap_openvas.h: GPL-2+ misc/pcap_tests.c: GPL-2+ misc/plugutils.c: GPL-2+ misc/plugutils.h: GPL-2+ misc/scan_id.c: GPL-2+ misc/scan_id.h: GPL-2+ misc/scanneraux.h: GPL-2+ misc/strutils.c: GPL-2+ misc/strutils.h: GPL-2+ misc/support.h: GPL-2+ misc/table_driven_lsc.c: GPL-2+ misc/table_driven_lsc.h: GPL-2+ misc/vendorversion.c: GPL-2+ misc/vendorversion.h: GPL-2+