Yes, and sort of.
Baby led weaning is an attitude. It means you are not going to get stressed out, you are going to let your baby take the lead, hence the name. So, if he seems ready for food before the golden 6 months, then yes, you can start before 6 months. But be careful you don't mistake his natural curiosity for being "ready". Babies are interested in everything. He probably watches while you brush your hair and put deoderant on, but that doesn't mean you'll be making him an appointment at Vidal Sassoon, and picking up a Lynx spray for him at the supermarket, so don't assume you need to give him food just because he watches you eat.
If however, he has doubled his birthweight, can sit up unaided, reaches for toys and puts them in his mouth, AND he's getting closeish to 6 months, then you might let him have a little play with some sticks of whatever.
Purees aren't banned, spoons aren't banned, but the key thing to remember is that you are letting your baby take the lead, which means he only eats if he wants to, and he stops when he wants. This is pretty hard to judge if you start by spoon feeding at first, and also sets up your expectations that he "needs" a certain amount of food - which may be hard for you to give up if you want to switch to BLW when he's 6 months.
So in short, my advice is to start when you think he's ready, but make sure you start with finger food so that he can truly take the lead. And read Gill Rapley's book, and have a look on this brilliant forum
Have fun! 