BBOS provides a command line interface (or CLI) that lets you interface with the RP2040 board directly. This makes it possible to not only interact with the Pi but also handle practical functions like real-time debugging. https://github.com/mcknly/breadboard-os
The PX5 RTOS is ULTRASMALL (< 1KB for minimal use), enabling its use in some of the most memory-constrained devices. It is one of the smallest RTOSes available, requiring less than 1KB of FLASH and 1KB of RAM on typical 32-bit microcontrollers. I have not found out how it is licensed.
The company also offers https://px5rtos.com/px5-net/, a TCP/IP implementation.
C-based Slack bot
For the C version, the following libraries will be used alongside the pico-sdk:
The C-based parts use the follolwing components:
FreeRTOS kernel – to provide a Real-time Operating System (RTOS) for the networking stack
lwIP – for TCP/IP communications
Mbed TLS – for TLS communications
coreHTTP – for the HTTP client
cJSON – for parsing and serializing JSON data
Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are Posix and ANSI standards. Additional standard APIs from Unix and other common RTOS’s (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).