On April 3, 1995, Emmet P. Gray,[1] an American programmer, at the time civilian employee at the US Army, now adjunct professor at the Texas A&M University,[2] released WRPN 1.0 (16-bit), a public domain open-source software written in Borland C++ 4.0 for early versions of Microsoft Windows.

[3][4][5][6] As of September 2024 the project is still in active development, and the latest WRPN 7.1.1 was released on August 26, 2024, for modern operating systems with Java installed, and as a mobile application for Android.

[7] WRPN simulates almost all of the functions of HP-16C: In 2019 Bill Foote, an American software engineer and ex-Lead of the Sun Microsystems' standardization of interactive technologies for Blu-ray and other TV platforms,[8] created the JRPN (JOVIAL Reverse Polish Notation Calculators), an open-source HP-16C simulator, forked from WRPN 6.0.2 in Java, but with all of the text set to be rendered from vector fonts (instead of the bitmap font used in WRPN), and licensed it under the free Apache License.

[9] I always wanted a 16C, but I never really needed it, and I was a starving student at the time :-) WRPN works great on Android, but the UI uses images that were created back when screen resolutions weren't so high, so I dropped Emmet a line, and re-did some of the UI and published that as what I'm now calling "Legacy JRPN".During the COVID-19 pandemic Foote fully rewrote JRPN code in Flutter and licensed it under GPLv3.

[10] JRPN is available now in two variants, 15C and 16C (simulating HP-15C and HP-16C accordingly), for Android, Linux, Mac OS, Windows and as a web application.