No, IPB is not free, although IPB 1.3 is used on hosts providing free IPB hosting such as IPBFree, although you can tell whether it's free or not as most of them would have "Powered by """ or "Free hosting powered by """.
I agree with thedudeman if you can afford IPB 3 then go for it, it's an amazing software and well worth the money. Yeah IPB 1.3 is full of massive secruity holes 😛.
It is a great bit of software. If you want to use 1.3 then use a free host as many have customized it alot and fixed the security problems. Don't download it and install it yourself as it is bad security wise as 1.3 is many many years old.
Erm, no it's not. You get what you pay for, compare it to web 1.0 vBulletin and their crazy price rises and then let us know if it's overpriced. You are not permitted to download 1.3 as it isn't supported, £75 is a small fee for one who has a solid niche, a fantastic idea and is very dedicated.
To some people, that is alot of money just for the software where there is many decent free forum softwares around that would do what they want and offer what they need.
To me right now, both IPB and vB are a waste of money for my needs, phpBB and MyBB suit me just fine.
However, everyone's needs are different. IPB is great software and well worth the money if you feel you have a strong enough need to switch to paid software.