+1'd just because I think Haskell is a cool language and would love to be able to spend more time learning it!
There isn't enough space on a small gear to install GHC, so we can't add this as a custom cartridge (I've tried) - it really needs to be in the host system.
Gideon, that's awesome. You can also create a quickstart and reference the URL directly in the cartridges spec so that you're searchable in the website (in the readme I see you're pointing directly to the from scratch page which is exactly what we wanted folks to do as well).
If you set the Cartridges field in the quickstart to:
The web UI will know how to handle it. Also note the use of the anchor - you can throw an anchor on any cartridge URL and the web UI will use the anchor as the "name" of the cartridge to display (you can do that with your custom cart spec).
Should this be added to https://www.openshift.com/developers/download-cartridges#examples?