It's been battle tested, all the issues in the article are solved (proper pruning, optimal results). Furthermore, its likely to have less bugs than the authors.
Its been tuned over years for use in competitions. So it probably runs faster than the author's, even though it has more features.
It uses a derivative of the same language the author has suggested (STRIPS is the predecessor to PDDL). So its basically the same interface but more general purpose. Using a standardised language makes the overall system more maintainable
There are no licensing requirements, because its a shell script. If you want to modify the solver then its GPL, but you want to pipe data out of it its ok to invoke it in a separate process.
I agree programming stuff is useful for learning. But optimization is specialised and tangential to most companies core competencies. Leave it to the professionals. You don't write your own SQL query interface for example (which is quite a similar problem).
EDIT:
The author should not feel like they made an obvious mistake though. The planning community is the worst for writing their software up in human readable form. Its really very easy to use, but you would not be able to guess that from their websites, their constant use of complex logical constructs every other sentence is infuriating.