How did it compile locally?

worldedit-core/src/main/java/com/sk89q/worldedit/math/BlockVector3.java

@@ -29,7 +29,7 @@ import java.util.Comparator;
 /**
  * An immutable 3-dimensional vector.
  */
-public final class BlockVector3 {
+public class BlockVector3 {
 
     public static final BlockVector3 ZERO = new BlockVector3(0, 0, 0);
     public static final BlockVector3 UNIT_X = new BlockVector3(1, 0, 0);

worldedit-core/src/main/java/com/sk89q/worldedit/math/Vector3.java

@@ -31,7 +31,7 @@ import java.util.Comparator;
 /**
  * An immutable 3-dimensional vector.
  */
-public final class Vector3 {
+public class Vector3 {
 
     public static final Vector3 ZERO = new Vector3(0, 0, 0);
     public static final Vector3 UNIT_X = new Vector3(1, 0, 0);