This is great for a free product!
OpenQuest is an indie retroclone version of RuneQuest which could be described as a trimmed down RQ6/Mythras, yet with the flavour of classic era RQ2 and RQ3.
Quick character gen, simple combat rules, reasonable weapon lists etc and Basic Magic. Perfect for an old school session if you want to play a classic fantasy D&D or RQ game, and there's no need to buy the expanded version unless you want more equipment and magic
OQ is.a good taster to see if you want to invest in the more complex versions of RQ down the track, although there's certainly no need to do so.
There's also a few sword and sorcery scenarios available, so this is perfect as an entry point into simple, classless classic fantasy gaming.
The Basic Edition of the core rules is self-contained and free, so you can't get much better than that!