Well, you aren't technically allowed to share with your siblings anyways. Nor are you technically allowed to install on two computers.
If that's a deal breaker for you, then I guess that's that. Naturally they have to try to do something to stop outright piracy.
It does come with the added benefit (for the most part) of not coming with the "malware" that people hate such as Starforce.
The other alternative is the "limited download" paradigm that some online resellers use. Trymedia for instance, limited me to 5 installs with my licence for Eastside Hockey Manager. At first I hesitated, but then I figured that by the time I used up all 5 of my installs, I'd have likely gotten my $20 worth anyways (and I did...after 1 install). Still have 3 installs left.
EDIT:
Is this the Cthulhu game you were looking for?
<{POST_SNAPBACK}>
Technically I could uninstall every time I wanted to share with my siblings after backing up whatever saves there are, reinstall on whatever computer I/they're going to be using the game on, and I'd be within the confines of the EULA (I think). It makes more sense to me to do two installs and shuffle the discs around. It's not like we're both playing the game at the same time anyway.
EDIT: Bok I don't usually have a disc in the drive anyway. It kills the drive's longevity and it's a major power drain on my laptop. My conscience is clean, all my games are legit, but I generally use NoCD cracks.