I'm posting the bug here, because every other 0install app works in this setting.
Attemting to start dispcalGUI launches the 0install updater, which fails with the message quoted at the bottom. Pinging the IP in question fails with the packets dropped. Pinging that IP from another location using SSH works.
Thus, using dispcalGUI is not possible, at least not in Nigeria.
Other potentially 'problematic' IP ranges are probably also affected.
0install error message:
[17:11:20] Zero Install Command WinForms GUI started with: run --no-wait http://dispcalgui.hoech.net/0install/dispcalGUI.xml
[17:11:50] ERROR: Failed to download http://dispcalgui.hoech.net/download.php?version=2.6.0.0&suffix=.tar.gz.
Unable to connect to the remote server[17:11:50] ERROR: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 197.155.77.8:80
If your ISP blocks certain IP ranges, that's the party you need to contact. Even if SourceForge was responsible, there is nothing I could do about it, as I'm not working for them.