This company was started when it appeared that HEC-1 was to be replaced by HEC-HMS. Having reviewed the upgrade it was clear that HEC-HMS was not as good a program as HEC-1. HEC-1 was easy to follow and make adjustments on the fly. It had the ability to run several plans and ratios quickly.
There are a large number of Engineers that use HEC-1 but since it had been abandoned by HEC - the world needed this support.
Further, having worked with newer programs such as HydroCad, it was still clear that HEC-1 offered more; it had a history of acceptability throughout the world - and it was free!
Almost all hydrology programs use the same underlying computations - so using HEC-1 was not implying the use of some outmoded technology.
RGM HEC2000 was written to make life easier for Engineers and Hydrologists. In fact, our program sells internationally to many grateful clients.
The only real objection to using HEC-1 was that it outputted no decimal values since it had been set up originally for large watersheds. We fixed that by recompiling the software and we provide a new HEC-1 executable (the 2010 Version).
In sum, no other program has the flexibility of HEC-1.