Aspia is described as 'free and open source application for remote computer management' and is a Remote Desktop tool in the network & admin category. There are more than 100 alternatives to Aspia for a variety of platforms, including Windows, Linux, Mac, Android and iPhone. The best alternative is TeamViewer. It's not free, so if you're looking for a free alternative, you could try Chrome Remote Desktop or Remmina. Other great apps like Aspia are AnyDesk, DWService, mRemoteNG and UltraVNC.
Remmina is a remote desktop client written in GTK+. Remmina primarily targets system administrators and travelers that need to work with computers remotely in front of either large monitors or tiny netbooks.
DWService is an half (only the client/agent) open source project which offers a service that allows access to remote systems (Windows, Mac, Linux, Raspberry...) using a standard web browser - without any component required on the client side.
UltraVNC is easy to use and free software that can display the screen of another computer (via the Internet or a local network) on your own screen. The program allows you to use your mouse and keyboard to control the other computer remotely.
TightVNC is a free remote desktop application. With TightVNC, you can see the desktop of a remote machine and control it with your local mouse and keyboard, just like you would do it sitting in the front of that computer.