I have developed a website and which is using paid for components from the Elements Store.
If I work with a friend on the website, who has also has Elements, do we both need to purchase the paid for Elements Store Component that is used in the website for joint development?
For example, I may update the Elements project one day and my friend may update it on another day? This assumes we have some mechanism to make sure we aren’t both updating it a the same time; maybe using a GIT.
good question, and I would add.. both should work on the same versions, i guess.
You would need to use the same account logged into elements. In my understanding each account can be used on several Mac’s, but each account needs their own purchases
To set the scenario, this is working on a website for our club.
Can an account be used by more than one person at two different physical locations? Can it be used at the same time by two different people, even if it is the same account?
If so, can a purchased component be transferred to another account?
Probably needs @dan to chip in. 
Good questions. In short it works the same as the App store, and traditional software licenses.
An Elements account can be used on multiple Macs, but it’s tied to a single user. If two people are working on the same project, they each need their own Elements account and each account needs to own its own copy of any paid components used in that project.
Sharing one account between two different people is not supported, whether you’re in the same location or in different places. Simultaneous use on two machines with the same account also isn’t supported.
Paid components can’t be transferred between accounts.
If multiple people are collaborating on the same site on their own machine, then everyone needs to purchase the components they’re using.
Let me know if you have any more questions!
Edit: You can read the full store policy here.