Regarding the original question - even if it were OK from the legal point of view (and I don't want to comment on that, even though personally I wouldn't see a problem about it), I'd suggest not to.
I can imagine that one day, we can start to detect unauthorized use of avast! Free in companies (I can think of some simple heuristics to achieve that, at least for bigger companies) - and you may fall victim to such detection. Sure, you have the license, but it may be an inconvenience (and cost time) to sort that out.
Also, I suppose it won't be possible to manage the Free edition remotely (once the business console is released). Don't know if any other problems may arise... but I'd call the whole thing kinda "risky" - the Free version is simply not supposed to be installed in corporate environment, and one day (unspecified) troubles might appear.