The moment it is necessary to make changes to the standard Phorum distribution files or database structure to implement some kind of functionality, we are talking about a hack (even if the changes that have to be made are accompanied by a drop in module).

Although there is nothing wrong with writing hacks, the Phorum team wants to urge you to try if you can write a module before resorting to a hack. Especially if you are going to publish your changes to the public. Modules are the preferred way of modifying Phorum functionality, because that will make both upgrading your distribution and having your modification adopted by others easier.