I noticed the only port of E1M1 for Half Life was
this one that combined it with MAP01 from Doom 2, and even then it's a remake not a direct port. So I went ahead and did it myself.
The geometry is identical to Doom, save for slight layout changes I made to play better in deathmatch (a raised ceiling for bhops, widened windows for gauss jumping, opened up secrets for better player flow, etc).
I started development on this in mid-late November, but there's also been a whole lot of downtime and procrastination. If I had to guess this was probably only a week of work, and most of that is because this was my first ever map. Which oh yeah, I got some playtesting done but don't be surprised if there's some rough edges.
Included in the download is the bsp, all required assets (sprites, sounds, skybox, etc), the original .map file, and the custom WADs I made for this with the doom textures and such.
If you wanna host this map through the game instead of a dedicated server, I have the required files for a fastdl up on my website, just run the command
sv_downloadurl "http://wii.gay/files/fastdl"
I have a blog post up on my site about how I made the map, you can read that
here. Also has a download mirror.
Credits are in the readme, but feel free to modify the map, port it to other games, fix any mistakes I made, etc. Just credit me and link back here.
Doom can run everything