Bonus: I took a look at the MARC relator terms used on CRAN (code here)
+------+--------------------+------------------+
| code | CRAN packages with | term |
+======+====================+==================+
| aut | 4868 | Author |
+------+--------------------+------------------+
| cre | 4800 | Creator |
+------+--------------------+------------------+
| ctb | 1531 | Contributor |
+------+--------------------+------------------+
| cph | 769 | Copyright holder |
+------+--------------------+------------------+
| ths | 117 | Thesis advisor |
+------+--------------------+------------------+
| trl | 53 | Translator |
+------+--------------------+------------------+
| fnd | 38 | Funder |
+------+--------------------+------------------+
| dtc | 31 | Data contributor |
+------+--------------------+------------------+
| com | 14 | Compiler |
+------+--------------------+------------------+
| ctr | 13 | Contractor |
+------+--------------------+------------------+
| rev | 11 | Reviewer |
+------+--------------------+------------------+
| anl* | 1 | Analyst |
+------+--------------------+------------------+
| ccp* | 1 | Conceptor |
+------+--------------------+------------------+
| res* | 1 | Researcher |
+------+--------------------+------------------+
Interestingly less than half of packages use them at all (there are over 12K packages). Also very few (just 3!) packages seem to have slipped through with a disallowed role:
+------------+------+
| package | role |
+============+======+
| CreditRisk | anl |
+------------+------+
| CreditRisk | anl |
+------------+------+
| rEDM | ccp |
+------------+------+
| rollmatch | res |
+------------+------+
| rollmatch | res |
+------------+------+
| rollmatch | res |
+------------+------+
| rollmatch | res |
+------------+------+