Actually the current run-time version has removed the 2M record limitation and provided many other features not available in earlier release(s).
The bigger issue is moving away from the proprietary database to PostgresSql, MySQL, or some other format which facilitates integration with ad-hoc queries and web application.
The first attempt at a different database was a switch to Faircom's C-tree format which worked well but there was little demand for this solution.
Frankly, the development of DecisionPlus was driven more by the application requirements of PaperTraq, MetalTraq (Yarde Metals is a client), and numerous other highly customized systems that addressed industry specific requirements provided by DecisionTree Systems from 1987-2002. The products are still supported by a group of consultants in North America. firstname.lastname@example.org is the contact for the latest info.