are all commercial components meant for single domain use?

hello , please want to ask if purchasing a commercial compoonent allows me to use it on more than one domain.
I am a web designer and want to deploy several opencart installations for my clients. do i need to buy an license for an extension for each clients website?

Apparently, yes. Unless the developer stated you can use on more than one website. Usually, you get a license or you purchase multiple times.

Depends on the individual license. My modules are "per-owner" so any sites that you personally own can use the module.
Other devs prefer per-domain.

Just wanted to clarify what MarketInSG said: the OpenCart store license for extensions is per-domain (or per-subdomain), unless the developer states otherwise, and you have to agree to the licensing terms when purchasing. This means you need to purchase a copy of the extension for each domain you install it on.

Most developers sell their extensions on their own site, as well, and the licensing terms there vary. So if you're looking for more lenient licensing terms, I would search there first, or contact the developer(s) of the extensions.