Enhanced SNACC http://esnacc-ng.org
A: eSNACC is the Enhanced Sample Neufeld ASN.1 C Compiler. It is a libre project with the goal of producing an ASN.1 to C/C++ (and more) code compiler. ASN.1 is a standardized language maintained by the International Telecommunications Union. The goal of ASN.1 is to produce a language which describes various types of data, and defines the framework by which that data is serialized and deserialized.
A: eSNACC can support most of X.608/X.609 for Basic Encoding Rules. Some notable exceptions exist (there are a few compliance issues with string formats and internationalization).
A: Currently, eSNACC targets C and C++ languages. There are some outstanding efforts to provide back-ends for python, java, C#, and go.
Note that not every feature may be available in every language. For example, some encoding rules may only be implemented in one language. In these cases, the documentation should explain the differences.
A: There is a good amount of support for Basic Encoding Rules. Some Distinguished Encoding Rules and Packet Encoding Rules support exists, but it is very early stages. Work is currently underway to enhance this and provide DER, PER, XER, and GSER support both in C and C++ languages.
Other encodings will be added. The best way to get your favorite encoding
is to write a new set of support libraries and add the code generation. Then
submit it as a patch (hopefully with tests for make check).
A: A bit of history. The SNACC project began back when free licenses were not fully vetted. The original code was licensed as both LGPL and GPL, but this was not workable (it would create a piece of code that was always GPL'd).
It was relicensed for 1.1 as GPLv2 for the compiler, and "Free Software" for the library. Although it is a bit fuzzy, the understanding is that this means you are free to run this work, modify this work, redistribute this work (including your modifications), and study the code this work (where this work means the parts of code which make up 'the library').
In 2002/2003 timeframe, DigitalNet (a now defunct branch of Getronics) took the SNACC code and enhanced it to include better support for C++, and newer ASN.1 syntax. These enhancements were added under the eSNACC Public License under contract to the US government. They codify the 'Free Software' license referenced above (although, obviously do not re-license the software).
A: Yes. If you incorporate the eSNACC compiler, you will be subject to the terms of the GNU GPL v2. If you only use the compiler to generate code and then use the resulting code and support libraries, your new work can be licensed however you like.
A: A little bit, yes.