It is possible that the conditions of Oracle Maven have changed. You may need to re-register on the Oracle Maven website: http://www.oracle.com/webapps/maven/register/license.html
I tried your github script and it worked fine with me:
$ mvn clean install
[INFO] Scanning for projects...
[INFO]
[INFO]
[INFO] Building mavensampleoraclejdbc 1.0.0-SNAPSHOT
[INFO]
[INFO]
[INFO]
[INFO] Deleting /Users/jean/Downloads/MavenOracle/MavenSampleOracleJdbc-master/target
[INFO]
[INFO]
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/jean/Downloads/MavenOracle/MavenSampleOracleJdbc-master/src/main/resources
[INFO]
[INFO]
[INFO] No sources to compile
[INFO]
[INFO]
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/jean/Downloads/MavenOracle/MavenSampleOracleJdbc-master/src/test/resources
[INFO]
[INFO]
[INFO] No sources to compile
[INFO]
[INFO]
[INFO] No tests to run.
[INFO]
[INFO]
[WARNING] JAR will be empty - no content was marked for inclusion!
[INFO] Building jar: /Users/jean/Downloads/MavenOracle/MavenSampleOracleJdbc-master/target/mavensampleoraclejdbc-1.0.0-SNAPSHOT.jar
[INFO]
[INFO]
[INFO] Installing /Users/jean/Downloads/MavenOracle/MavenSampleOracleJdbc-master/target/mavensampleoraclejdbc-1.0.0-SNAPSHOT.jar to /Users/jean/.m2/repository/com/github/sgrillon14/mavensampleoraclejdbc/1.0.0-SNAPSHOT/mavensampleoraclejdbc-1.0.0-SNAPSHOT.jar
[INFO] Installing /Users/jean/Downloads/MavenOracle/MavenSampleOracleJdbc-master/pom.xml to /Users/jean/.m2/repository/com/github/sgrillon14/mavensampleoraclejdbc/1.0.0-SNAPSHOT/mavensampleoraclejdbc-1.0.0-SNAPSHOT.pom
[INFO]
[INFO] BUILD SUCCESS
[INFO]
[INFO] Total time: 0.900 s
[INFO] Finished at: 2018-02-12T17:06:49+01:00
[INFO] Final Memory: 12M/309M
[INFO]
wagram:MavenSampleOracleJdbc-master jean$