blackpoint is licensed on a per server basis (which is different than the default blackpearl license which is per user), so if you install it on multiple servers, you'll need multiple licenses.
You must install the SharePoint components on all of your WFEs (this doesn't require a server license). You must install the server components on at least one server (you need a blackpoint license for each one you install it on). The only reasons you install the server components on multiple servers are for redundancy or performance. Just because you have multiple WFEs doesn't mean you have to install the server components on multiple servers.
All that matters for your WFEs to function properly is that you have installed the SharePoint components on each of them and that the server components have been installed on at least one server somewhere which is accessible from your WFEs.
As far as which server(s) to install the server components on, a lot of factors come into play such as how heavily utilized the machine already is, how many workflow instances will be active at any one point, etc. There isn't a single, one size fits all answer, but it is important to recognize that workflow processing takes up CPU, RAM, IO, etc., on whatever machine(s) you install the blackpoint server components on.
If you expect to have tens of thousands of active process instances, you'll probably want to give it its own dedicated server(s) or if your WFEs are serving thousands of users a minute, again, the WFE probably isn't the best place to be running the server components. But if you have only a few hundred active processes or are only serving a small number of users then you won't have a problem with your WFE(s) running the server. It really just depends on your situation.
Colin
K2 Insider
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