Hewlett-Packard has outsourced its calculators to this company.

Found on the MoHP forum

The RAN # function of HP-11C and -15C computes
 x_{i+1}=(33(29⋅2010667⋅x_i+131⋅449⋅641)) mod 10^{10}

Includes a link to https://technical.swissmicros.com/doc/pdf/Bairstow.pdf

Python to RPN converter for generating programs for the HP42S and DM42 calculators (and emulators like Free42).
From https://www.hpmuseum.org/forum/thread-10178-post-177378.html#pid177378
MIT licensed according to README.md

Simulators for the hp15c and hp16c calculators, can be used in the browser or as Android app(lication).

Program to determine the calibration value needed to correct for the frequency error of dm42s' RTC.

The HP 48 object listed below in ->ASC form is a high-performance polynomial root finder. Those of you who remember the HP 71B Math Pac will recognize this as the same as the PROOT command from that Pac; it is in fact the same assembly-language code, given an RPL front end to operate in the HP 48.
Found on https://www.hpmuseum.org/forum/thread-10967-post-160700.html#pid160700
See also http://www.jeffcalc.hp41.eu/emu71/mathrom.html#src for the uncommented source code of PROOT and other functions of the HP71B math pack.

HP-15C Simulator for Windows, Linux and macOS. Supports data exchange with SwissMicros https://www.swissmicros.com DM15 models.

Perl program to convert {dm,free,HP}-42 programs from textual representation to raw files which can be loaded into {dm,free}42.