The Apple Macintosh has been heralded as one of the most user friendly computing platforms ever, with its full vertical integration of hardware, software, and peripheral devices. The Apple Macintosh, and Mac OS, are typically the epitome of user friendliness and accessibility. But, Apple being a business, effectively locks out older hardware from modern software bliss. Ironically, I had to install the most open source operating system in the world, one targeted at tech-heads and developers, to get my 2006 MBP running again at decent speed with more modern applications.
That said, one of my go-to apps is Remember the Milk, which I use to manage my day to day activities. Luckily, RTM has a Linux version. I run Debian, and RTM offers an Ubuntu version. This makes sense since Ubuntu is arguably one of the friendlier and more accessible Linux distributions. But, Ubuntu is built on Debian, so when RTM releases their app as a .deb package, this means I can download it. Woot!
Conventionally, I use apt-get.. I’m still wading in the shallow end of the Debian pool, but you can install a .deb file manually (i.e. without apt-get); this is mainly because apt-get is a front end to the Debian package manager, dpkg.
That said, thank you Ask Ubuntu @ Stack Exchange:
sudo dpkg -i DEB_PACKAGE
sudo dpkg -r PACKAGE_NAME
Now, RTM is happily running on a 11 year old laptop that the manufacturer has all but abandoned, thanks to some great open source software.