Hey there folks, I hope this question isn't too confusing. I also hope it's not against any forum policies. I have two MacBook Pros and one of them is currently used by my mother. I gave it to her as a gift and upon giving it to her, I signed her in to her own Apple ID for the Mac App Store so she can buy her own apps. My question is- Could I log in to the Mac App Store with my ID for the purpose of installing Lion on her Mac, but then log her back under her own account? And if I do this, will it screw up Lion? Thanks in advance for any help!
Short answer: Nope.
The user agreement allows you to install the software on as many devices as you like <provided> they are all using the sam Apple ID. If you were to login to your own account in order to redownload Lion onto your mother's computer, you'd have a problem logging her back into her own ID. She'd lose access to apps and her iTunes-purchased content.