Let us assume we have an Ethereum contract to issue software licenses. The contract creates an entry in it's local database to document the availability of the license to the purchaser. In which way should the issuer of the license check if it has been granted? Typically I would want to check this at runtime from within the licensed piece of software.
So more precisely the question is: What is the intended way for a third-party client to query the blockchain if the queries have to be run quite frequently and refer to potentially "old" data?
One commenter doubted that it may be useful to involve a blockchain at all in this task and asked for a motivation. One motivation might be that by putting license information into a blockchain you avoid distributing proprietary license files, which might open a path to a more generic way of software licensing. Furthermore, you do not have the license server as a single point of failure. And, as already pointed out by the commenter, the technical use of license would not be prevented even if the issuer goes out of business.
