You can get it by adding this to your /etc/apt/sources.list:
deb http://logjam.danga.com/download/deb/ ./
And then run the usual apt-get update and apt-get install logjam.
I can't see why this wouldn't work on Debian, too -- please let me know if you try it and it works. My Ubuntu versions will supersede the corresponding Debian package, but newer Debian packages will replace my Ubuntu package.
If you're using the Ubuntu (or Debian experimental) version of apt, you'll get a complaint about verifying the archive. You can just hit "y" to install the file, or you can learn more about apt's signed archives.
To eliminate the warning, you'll need to:
- Get my GPG key into apt. You can fetch my key with gpg --recv-keys DED37B19 or by cut'n'pasting it from my LiveJournal public key. (Whether to trust this key is a security decision you'll have to make on your own...)
- Push my key into apt, with a command like gpg --armor --export DED37B19 | sudo apt-key add -