From the developer's website: "PDF Browser Plugin 2 is free for not-for-profit activities if used at home or at educational institutions" - Yes, £69 is a lot when Acrobat is out there for free (but give me PDF BP anyday), but by charging this amount, I assume that the developer can subsidise his development of a tool that people like me or my students can use for free. If you're using it for profit, then pay for it out of your profits...