Serial communication component for .NET.

communication with any device connected to serial port
easy of use and very powerful
uses multithreading and overlapping for maximum performance
available for .NET 2 - 4.7
source code included in registered version
royalty free distribution in applications

.NET component for accessing Windows I/O and memory-mapped ports.

access to I/O and memory-mapped ports on 32 and 64-bit Windows
PnP device drivers built using Microsoft KMDF WDK framework
easy of use, component is fully autoconfigurable
block data transfer enables high speed data transfer
DirectAccess mode provides the fastest access to I/O ports (32-bit Windows only)
available for .NET 2 - 4.7
royalty free distribution in applications

FireMonkey implementation for Linux
Start build UI Linux apps with Embarcadero Delphi and FmxLinux

Delphi and C++ Builder components for preparing and burning images to CD, DVD, and Blu-ray optical storage media.

uses standard Windows Image Mastering API 2
available for Delphi/C++ Builder 5 - 10.2 and Lazarus 1.8
source code included in registered version
royalty free distribution

WebStorm brings you smart coding assistance for jР°vascript and compiled-to-jР°vascript languages, Node.js, HTML and CSS. Enjoy code completion, powerful navigation features, on-the-fly error detection, and refactorings for all of these languages.

There are quite a few Delphi open source projects on GitHub that can really save you some time. I searched for Delphi on GitHub and then sorted by the Most Starred projects and came up with this Top 10 list. There is some really good stuff here including Awesome Delphi (which is another top list), Delphi IDE color theming projects, an MVC web framework, a REST API client, Open Source Computer Vision Library headers for Delphi, a really powerful custom TreeView component, a unit testing framework, a component for embedding Chrome in your app, and finally the fantastic OmniThreadLibrary.

Components for viewing, navigating, text extracting and editing PDF files.
uses PDFium open-source PDF rendering engine
available for .NET 2 - 4.7
source code included in registered version
royalty free distribution in applications

Communication protocols 3964 and 3964R for .NET.
available for .NET 2 - 4.7
source code included in registered version
royalty free distribution

Use OCR.NET component to retrieve text from image, for example from scanned paper document.

uses Tesseract OCR engine and Leptonica image processing library
available for .NET 2 - 4.7
source code included in registered version
royalty free distribution in applications

uses ZBar bar code reader library
supports EAN-13/UPC-A, EAN-8, UPC-E, Code 39, Code 93, Code 128, Codabar, PDF417, GS1 DataBar, GS1 DataBar Expanded, Interleaved 2 of 5 and QR Code barcodes
available for .NET 2 - 4.7
source code included in registered version
royalty free distribution in applications