Q: "Own and control" clarification please

My interpretation is that the "you" in the verbiage refers to the person whose Apple ID is being used to obtain the software. So, you can download/install it on any computer "you" own or control. If a family member has their own Apple ID on a different machine and it is registered in their name, then technically, that is not "you". However, with family members, the issue becomes a bit murky and could be argued either way by two different lawyers. On the other hand, it would not work if someone with a different Apple ID were to try to download it and frankly, I do not know if you could install it on a machine which was registered with a different Apple ID as I've never tried it. The issue would be less murky if it was one computer, but here you want to install it on two. My take: you need to purchase it twice.

If you want to know definitively, contact Apple legal as we are all other users with different opinions or interpretations of the legalese.

ambiguous

That gives the legal profession the opportunity to argue things either way - depending on which side they're representing... and the consumer is left to "interpret".

I don't pay too much attention to those over-simplified FAQ's; the only thing that really counts is the legalese in the SLA. Here is the FCP X SLA:

http://images.apple.com/legal/sla/docs/FinalCutProX.pdf

And here is the excerpt from the iTunes Usage Rules referenced in the above:

MAC APP STORE PRODUCT USAGE RULES

Except as otherwise set forth herein,

If you are an individual acting in your personal capacity, you may download and use an application from the Mac App Store ("Mac App Store Product") for personal, non-commercial use on any Apple-branded products running Mac OS X ("Mac Computer") that you own or control.

(ii) If you are a commercial enterprise or educational institution, you may download a Mac App Store Product for use by either (a) a single individual on each of the Mac Computer(s) used by that individual that you own or control, or (b) multiple individuals on a single shared Mac Computer that you own or control. For example, a single employee may use a Mac App Store Product on both the employee’s desktop Mac Computer and laptop Mac Computer, or multiple students may serially use the Mac App Store Product on a single Mac Computer located at a resource centre or library. For the sake of clarity, each Mac Computer used serially by multiple users requires a separate licence.

(iii) Use of Mac App Store Products may require sign-in with the Apple ID used to download the Mac App Store Product from the Mac App Store. Mac App Store Products can be updated through the Mac App Store only

There's also a bit in SLA, for FCP anyway, that the license is not transferable.

Yep - the individual SLA's for the various applications are the definitive legalese anyway; that is mentioned in the iTunes/MAS terms as those terms are really geared towards "content" (music, movies, etc).