ABNF, the grammar definition for parsers generated by APG.
IETF tools page
APG and other ABNF are tools listed here.
IETF RFC page
The jump-off to all of the RFCs.
The Linux home page with distributions, tutorials and more.
What is Ubuntu? From the Ubuntu FAQ -
Ubuntu is a complete Linux-based operating system containing the very best free and open source software applications you need to work and play. With Ubuntu you can surf the web, read email, create documents, presentations and spreadsheets, edit images and more.
(Ed. You can also develop and run APG applications.)
SmallMGC is an Open Source Media Gateway Controller for access and residential gateways. APG is the parser of choice for SmallMGC's MEGACO message handling. If you are interested in Next Generation Networks, check out SmallMGC.
An excellent source of definitions and further references to just about everything you might want to know about parsing algorithms and who knows what else. Its list of parser generators has links to over 100 parser generator products, including APG.