Just because Broadcom won't sell them doesn't mean the factory won't make some more. This is China, they have a pretty liberal (and one could argue: more reasonable) approach to issues of intellectual property :).
Or at least it used to be so; sadly, in the last few years the US was pressuring Chinese government to crack down on it. Anyway, you can read more about this phenomenon here: [0].
Oh, and one more thing. It may not apply to RPi in terms of cloning it because it's still quite a niche product, but in general, they actually recycle electronics here. Like, seriously, when you throw away your smartphone, it'll likely end up in China for desoldering. So will your laptop. The amount of desoldered components and especially ICs available for sale is staggering. I have no data for this, but I'm pretty sure people here are making small-scale production runs out of recycled ICs. So Broadcom may not sell you their chip, but the lady on the first floor of SEG building in Shenzhen just might.
BTW., I love how they recycle components so much, and how it leads to interesting situations sometimes. For instance, I recently got my phone fixed - $15 and 15 minutes of waiting was all it took to get the front half of Galaxy S4 replaced with a brand new part (screen + touch surface + glass + box) and to get a new camera (electronics, lens and all). The equivalent repair at home would cost me around $240 and would take a few days. The secret of such cheap and fast repair? They took the broken parts from me. They'll regain 90% of value of that repair by simply replacing broken subcomponents in their own time, and then pushing the fixed modules back onto the market.
[0] - http://www.bunniestudios.com/blog/?cat=20