Submitting to the IETF requires that code snippets be licensed under the
BSD. The BSD license allows for free use of the code. You can use the
specifications and code in any software product. I know that Windows,
Linux, and Mac all use some BSD licensed code.
ABNF is Augmented Backus–Naur Form. ABNF defines a grammar that can be
used to create a parser. Section 4.2 of the document supplies the ABNF
for SignWriting Interchange. This ABNF grammar can be used to create a
parser that will read and validate data.