I know that when I buy Opus, I can install it on my laptop too. I'm using good desktop but really old laptop (using rarely when I travel). Can I install Opus 12 on my desktop and, for example, Opus 9 on laptop (if it turns out that Opus 12 is too heavy for this machine)?
Opus 12 isn't really 'heavier' than Opus 9 so I doubt you would want to do that, unless the laptop is running a really ancient version of Windows (Win95, Win2k) which newer versions of Opus no longer run on.
But to answer the question, quoting some parts of the Licencing FAQ:
[ul][li]Your Opus 12 licence can be used with Opus 11 (or even Opus 10 or 9) if you really want.
[li]Please email email@example.com if you have a question relating to licencing, purchasing or upgrading that isn't covered [by the rest of FAQ].[/li][/ul]
I've read that faq before I wrote this post. My question was about different verson on desktop and laptop. In faq I read about old version installed on both computers (if someone doesn't like for some reason newer version). But if you said that O12 is not heavier than O9 then is ok.