It's interesting to note that in the context of this letter about the Journal of Algorithms, that there is now an open-access journal called "Algorithms" which looks like it launched five years after this letter:
With a different set of problems imo. MDPI is a for-profit publisher with a "pay-to-publish" model, charging authors $1800 per accepted paper. And also a mixed reputation on quality, verging on a "paper mill" where they accept anything just to maximize their publication fees. Not a great model imo. There are non-profit Platinum OA journals that don't charge publication fees, like JMLR (https://www.jmlr.org/), which is the only kind of OA I consider interesting.
https://www.mdpi.com/journal/algorithms