airframes.org bans the use of 'bots' for lookups, so an agreement would definitely be needed.
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No bots, please ...
No bots, spiders, scrapers, scripted or otherwise automated queries, please.
As an exception, bots are tolerated only as long as they respect the robots.txt standard and if their purpose is to index this site to be included in a public search engine. And that is just a handfull like Google, MSN, Yahoo, etc.
Spidering this site violating this rule by sending private harvesting bots or otherwise sending automated queries is considered abuse. Violating bots will be blocked and/or publicly listed.