1. Info
The Rad-Therapy project produces a freely available, multi-platform QuakeC-based HL DLL replacement. Our efforts place emphasis on data-oriented design, portability, standardization, correctness and customization. It also offers multiple reference ports of popular modifications:
- Counter-Strike/RetroCS
- Deathmatch Classic
- Team Fortress Classic
- They Hunger
- Opposing Force
- Poke646
- Scientist Hunt
- Zombie Panic!
This is made possible with the Nuclide project by Vera Visions L.L.C. and the FTE QuakeWorld engine.
2. Downloads
If you already have FTE QuakeWorld for your platform:
Latest release (03-22-2024),
save it into Half-Life/valve/
Addons
Counter-Strike (03-22-2024),
save it into Half-Life/cstrike/
Gunman Chronicles (03-22-2024),
save it into Half-Life/rewolf/
Opposing Force (03-22-2024),
save it into Half-Life/gearbox/
Poke646 (03-22-2024), save it
into Half-Life/poke646/
Scientist Hunt (03-22-2024),
save it into Half-Life/scihunt/
Team Fortress Classic
(03-22-2024), save it into Half-Life/tfc/
The Specialists (03-22-2024), save
it into Half-Life/ts/
They Hunger (03-22-2024), save
it into Half-Life/hunger/
3. Screenshots
This image was created for use on this site using components taken from Half-Life owned by Valve Corporation. The copyright for the components are held by Valve Corporation while the copyright for these particular compositions are held by us.
4. Installation
Extract the release archive, merge the contents of the folder inside the tarball with your Half-Life installation.
You can then proceed to run the game with the RadTherapy script.
The engine should also automatically detect HL1 when placed within the game directory, however you may need to pass -halflife just in case you have one massive directory with multiple FTE-supported games in it.
You can also launch mods like this: fteqw.exe -halflife -game cstrike
5. Building
Be familar with the git program, and you can clone Nuclide, and then
within that directory clone the respective game repositories of your
choice.
Then issue: make game GAME=valve
to build the various pieces of game logic (in the form of QuakeC .dat files).
6. Credits
- Spike for FTEQW and for being the most helpful person all around!
- Xylemon for the hundreds of test maps, verifying entity and game-logic behaviour
- Theuaredead`, preston22, dqus for various patches
- To my supporters on Patreon, who are always eager to follow what I do.
- Any and all people trying it, tinkering with it etc. :)
7. License
ISC License
Copyright (c) 2016-2026 Marco "eukara" Cawthorne
Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
8. FAQ
There are thousands of games out there built as mods or standalone titles on the Half-Life engine.
That engine is old and in maintenance mode, is not licensed under any terms that make it accessible to developers who have the urge to build something within its development environment. This project already solves that problem. It offers a way for people to migrate to a software stack that is fully open, with no strings attached.
- Rad-Therapy is not HL1 and is not intended to 'replace' HL1.
- Be able to complete the game in singleplayer, and be aware of custom maps, mods and what they often like to do as well.
- It should also be compatible with whatever free or libre replacement data will become available in the future.
- It's not a port of existing sources, and is not compatible with mods unless they too are rebuilt.
- It meant to be used to build other games and projects, similar to what HL1 is.
- It's supposed to feel authentic to what HL1 was, but without the jank you don't care to remember.
It is all free. The binary releases are free, the sources are free. All parts of Rad-Therapy have reasonable copyright terms permitting free redistribution. You can do whatever you wish, including building a game with it and sell it on the Internet or in the real world. We only ask for attribution.
However you currently still need to supply the data files for Half-Life in order to really play this. That game is still under Copyright © Valve Corporation. You can find ways to purchase the game both physical and digital on frag-net.com along with the latest patch (which contain extra maps and addons). There is a project underway called Rad-Synth which aims to create a free replacement for the original data files. Stay tuned!
The developer is doing this for everyones benefit, even small contributions help in making a big difference.
Being built from the ground up with hindsight and other modifications in mind, it's a lot simpler to get started creating custom objects. You can design whole weapons, items, monsters (as well as their schedules) without writing a single line of code. This is due to Nuclide's data oriented design and the use of id Tech 4 style decl files.
Because it's built on Nuclide, it also has a different netcode, with weapon prediction standard across the board. There's also bots included with every game, as well as voting features and a metamod inspired plugin system, with a few ports of popular plugins.
Even gamerules can be swapped out on a whim, as they're simply external modules separated from the server to begin with.
Anything that the engine binary (provided by FTE QuakeWorld) runs on is supported. All components in Rad-Therapy are platform/architecture independent. Being a QuakeC project has that benefit. This generally means that unless you are making engine modifications for your project, you will not need to port your project.
We've successfully tested it ourselves on Linux, OpenBSD, and Windows.
It is mainly orchestrated by Marco Cawthorne which you can support on their Patreon. He also runs the frag-net game network that powers the on-line backbone of the project. Helping out with the costs that way is greatly appreciated. That said, expressing yourself in the Matrix chat can also nudge the project. If you're the type of person that knows exactly what we need and can lend a hand, be sure to reach out!
Rad-Therapy logo by Vera Visions L.L.C.;
This site Copyright © 2025, 2026 Rad-Therapy Project; FTE QuakeWorld is Copyright © 2002-2026 David Walton; Half-Life, and any associated characters belong to Valve Corporation. All Rights Reserved.
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