Top 3 on-premise Help Desk apps
Jitbit Help Desk is offered both as a SaaS solution and a "self-hosted" app as well. It has everything a helpdesk app needs - Knowledge-base, file-attachments, email integration - but also comes with some unique features like Google Drive integration, automation rules/macros and a nice "website-widget" (allows easily adding a "contact us" form to your website).
The system is very budget-friendly: only $899 for a lifetime license. The system is Windows-server based which means you cannot install it on a Linux-system, but you get all the perks of MS-architecture: Active Directory integration, MS Exchange integration (via IMAP), Windows-integrated authentication etc. The free Jitbit's iPhone/Android apps can be used with the on-premise system as well.
Just like the other systems in the list, it offers ticket categorization, prioritization, tagging, built-in search-engine, Knowledge-base, file-attachments and other features.
By the way, this is the only system that is also available with source codes.
Helpspot has been around for a while. It is a PHP-based "on-premise" ticket system from a company named UserScape. Helpspot comes with powerful email integration features, request management, customer self-service portal with a Knowledge-base and basic macros support ("if this do that" engine). The price is $239 per agent which is a lifetime cost.
Helpspot can be installed on a Windows server, even though it's PHP based, and it features some very basic Windows-authentication support. The system includes a reporting module allowing nice performance analysis to measure your support team effectiveness. Overall it's a very nice system but the user-interface looks a bit outdated.
Also a PHP/MySQL based system - Kayako - is the oldest player in the niche. It's being used at tens of thousands of companies, but we find the UI to be a little old-school. Though, after getting used to it, you'll find everything a modern help desk system needs - file-attachments, SLA rules, categories, Knowlegde-base, live chat and even VoIP integration for incoming calls.
The on-premise version of Kayako is kinda pricey, its $3000 per year for the 10-agent package.
UPDATE: as of 2016 Kayako has shut down their on-premise system any more, they went all-SaaS.
SysAid is a dinosaur. Some people find it old-school but it's a powerful "IT management" solution. So if you're into all those fancy abbreviations - ITSM, ITIL, CMDB - go for SysAid. But not if your company is too big - the pricing will kill you. It start from $500 for 1 agent. By the way, the company does not publish prices on their website, thay want you to call sales - bad sign.
SysAid comes with mobile apps, an asset management module, and is known for the ease of use, that's the "pros". Among the "cons" are: too many email notifications you get from it, no integration with 3rd party apps and lack of customizations.