() Articles related to ARINC standards and their use in FlightGear
Note that doesn't mean that we are not allowed to use freely available information - only that we would have pay for the specs if were to buy them from ARINC.
The J661 project is also based on ARINC (661) and still is open source ... and ARINC is even fully aware of it, because the j661 lead developer is on the A661 standards committee - so there's really no conflict here. Note that ARINC *drafts* are normally not charged for at all - and they still contain plenty of relevant information. 
- Hooray (Nov 23rd, 2012). Re: MD80 simulator based on Flightgear.