What does it do?
TTDPatch is a unoffical patch that modifies the way Transport Tycoon Deluxe works.
It offers many improvements in gameplay and offers a different way of experiencing TTD and it fixes bugs as well.
Is it a cheat?
Yes, as it changes a lot of aspects of the gameplay, but has so many other improvements you don't need to fear using it. Everything can be customized via TheConfig, so you can disable sign cheats as example or make them cost money.
Who made it?
TTDPatch was originally written by Josef Drexler, but today PatchTeam supports it. Many people have their own versions, for testing new features, etc. These experimental releases are only some of the PatchVersions available, and should be used with caution.
Is it free?
Josef Drexler released TTDPatch under the GPL licence.