Hammertime is an open-source Fork of Sledge which is an open-source Alternative to Valve's Hammer Editor for the Goldsource engine. It is written in .NET and uses Veldrid for rendering, with DirectX 10.
Hammertime supports Goldsource mapping, and is constantly being updated to add more Features, some of these Features include:
- Prefab Support
- Model exporting (Like Propper)
- Dragging Brushes like in Hammer 5.2
Here are also some good Community Editors if you need some:
- TrenchBroom (TrenchBroom is very prominent in the Quake Mapping Community, it is used by some people for Half-Life mapping, but theres not a lot of people using it.)
- Valve Hammer Editor (Found in the steam Library which you get when you own Half Life 1)
- JACK (Only get the paid Version if you want Steam Achivements.)
The Hammertime Editor is licensed under BSD-3.