Many users are still running sql-ledger 2.6.27 or older versions due of stability reasons and/or fear of upgrade problems. Sql-Ledger 2.8.17 is now stable enough and feature rich to make it worth upgrading.
We have some upgrade instructions at:
More help is available through sql-ledger mailing list or our support ticketing system (firstname.lastname@example.org). (You do not need to be our customer to request for support)
Users of business software prefer to stay with stable releases as long as possible. They do not risk their businesses to bleeding edge software. This is understandable. We have plans to support SL 2.8.x series with our own bug fixes and security patches for at least 2 years once the official support ends. This will be done with community help and our own resources.