Why? This is a miscommunication issue, not a CS issue. Determining whether or not something runs "infinitely" is typically just, "Does it run longer than an acceptable amount of time?" It may not actually run infinitely, but it may run practically infinitely (which is to say, just very long).

You have people responding that are assuming that they're going to test if a process takes too long and bail if it does. Pretty simple, actually, since for all practical purposes, when somebody describes a program as "taking forever," they rarely mean "forever" literally.

If you want to ask it, go ahead, but understanding practical limitations and engineering to those is a perfectly acceptable answer for the context of the rent-a-coder site (and an interview for a coding job). The only time it's not is if you're interviewing for some sort of academic position.