At one time, it was in the Baen Free Library ( https://www.baen.com/allbooks/category/index/id/2012 ) but it appears to have gone back to a regular "you buy it book". https://www.baen.com/wizard-s-bane.html
However, if you dig in Wayback, you can find the Free Library of old - https://web.archive.org/web/20050828182931/http://www.baen.c... and the first two (IMHO the best two) books. Its old school frame stuff to get it to the screen (which works) and linkable via going to the frameless version ( https://web.archive.org/web/20050903172506fw_/http://www.bae... )
The first 3 books can be found as one volume on Kindle https://www.amazon.com/Wiz-Wizardry-combo-volumes-Book-ebook...
As to recommending the book (and series)? Yes. The first three are good. Book 4 is... getting weird and 5 is weird.
So, is the book ‘Wizard’s Bane’ actually focused on using Forth (or some ersatz programming language concept) to do magic? If so, that basically describes a huge part of an hypothetical RPG I’ve been designing on paper since college. Also, would you recommend the book to a fan of genre fiction?