ZXing is an open-source, multi-format 1D/2D barcode image processing library implemented in Java, with ports to other languages.
ZXing wrapper is based on the ZXing.Net library.
Both are shared under the Apache License 2.0
Here there is an executable to encode/decode barcodes (example > unzip the ZXing.Net.DemoClients.Xarchive > WindowsFormsDemo >WindowsFormDemo.exe)