Install on Two Computers?

I am wanting to purchase AoE II DE to be able to play with my son (nostalgia and shared memories!), and to do so, will need to install on two computers so we can play against each other. If I purchase one copy of the game, am I allowed to install it on two different computers in our home so we can play each other, or does it require two separate purchases?

I found out each one can play with seperate Xbox live accounts, even if one is not original buyer but… I had crash issues on both LAN and multiplayer, and I couldn’t find out if it’s due to pure technical problems or license reasons.

I’m wanting to play over LAN with my family too. I would think that if it was a licence problem then the game would give a heads up instead of crashing to desktop. I bought the game specifically for multiplayer so I really hope that this crashing glitch is fixed or at least explained.